MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

1. A wire for use as a fuse was connected to a source of constant e.m.f. until the wire melted. The following graph of current I against time t was obtained. The circuit was switched on at t = 0 s.

(a) Explain why the current decreased during the test before the wire melted.

....................................................................................................................................................................

................................................................................................................................................................ [2]

(b) Determine the total charge that flowed during the test.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

2. (a) A lamp rated at 3.0 V, 0.25 A is connected to a 9.0 V supply of negligible internal resistance with a resistor R so that the lamp works normally.

SHK Page 1

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

(i) Calculate the resistance of the lamp when it is working normally.....................................................................................................................................................................

................................................................................................................................................................ [2]

(ii) Calculate the resistance of R.....................................................................................................................................................................

................................................................................................................................................................ [2]

(b) The lamp is now connected into a different circuit as shown below. The power supply is the same as before. The lamp is still working normally.

(i) Calculate the total resistance of this circuit.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

(ii) Explain which circuit dissipates the lower total power.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

SHK Page 2

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

3. The graph shows how the resistance of two components A and B varies with temperature.

(a) Identify the components.

A............................................................................................................................................................. [1]

B............................................................................................................................................................. [1]

(b) Explain, with reference to charge carriers and drift velocity, why the resistance of component A increases as the temperature increases, while the resistance of component B decreases as the temperature increases. You may be awarded a mark for the clarity of your answer.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

SHK Page 3

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

4. One of the functions of the 12 V battery in a car is to provide the energy for the car’s sidelights and headlights.

(a) The diagram shows the battery connections for four sidelights and two headlights.

(i) Each sidelight is rated at 12 V, 6.0W. Assuming the internal resistance of the battery is negligible, calculate the current in the battery when just the four sidelights are lit.

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

(ii) The power of each headlight is 48W. Calculate the combined resistance of the headlights.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

(b) The internal resistance of a car battery is not negligible but is designed to be as small as possible. Why is it necessary for the internal resistance of a car battery to be as small as possible?

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

SHK Page 4

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

5. (a) Explain what is meant by the diffraction of a wave.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

(b) (i) Outline briefly an experiment that may be used to demonstrate diffraction of a transverse wave.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

(ii) Suggest how your experiment in (i) may be changed to demonstrate the diffraction of a longitudinal wave.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

SHK Page 5

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

6. A potential divider circuit consists of two resistors of resistances P and Q, as shown in Fig. 6.1.

Fig. 6.1

The battery has e.m.f. E and negligible internal resistance.

(a) Deduce that the potential difference V across the resistor of resistance P is given by the expression:

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

(b) The resistances P and Q are 2000 Ω and 5000 Ω respectively.A voltmeter is connected in parallel with the 2000 Ω resistor and a thermistor is connected in parallel with the 5000 Ω resistor, as shown in Fig. 6.2.

SHK Page 6

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

The battery has e.m.f. 6.0 V. The voltmeter has infinite resistance.(i) State and explain qualitatively the change in the reading of the voltmeter as the temperature of the thermistor is raised.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

(ii) The voltmeter reads 3.6 V when the temperature of the thermistor is 19 °C.Calculate the resistance of the thermistor at 19 °C.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [4]

7. (a) State three pieces of evidence provided by the photoelectric effect for a particulate nature of electromagnetic radiation.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

SHK Page 7

Fig. 6.2

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

................................................................................................................................................................ [3]

(b) (i) Briefly describe the concept of a photon.

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

(ii) Explain how lines in the emission spectrum of gases at low pressure provide evidence for discrete electron energy levels in atoms.

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

(c) Three electron energy levels in atomic hydrogen are represented in Fig. 7.1

Fig. 7.1

The wavelengths of the spectral lines produced by electron transitions between these three energy levels are 486 nm, 656 nm and 1880 nm.

(i) On Fig. 7.1, draw arrows to show the electron transitions between the energy levels that would give rise to these wavelengths.

Label each arrow with the wavelength of the emitted photon. [3]

(ii) Calculate the maximum change in energy of an electron when making transitions between these levels.

SHK Page 8

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

8. (a) State what is meant by(i) the frequency of a progressive wave,

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

(ii) the speed of a progressive wave.

....................................................................................................................................................................

................................................................................................................................................................ [1]

(b) One end of a long string is attached to an oscillator. The string passes over a frictionless pulley and is kept taut by means of a weight, as shown in Fig. 8.1.

Fig. 8.1

The frequency of oscillation is varied and, at one value of frequency, the wave formed on the string is as shown in Fig. 8.1.

(i) Explain why the wave is said to be a stationary wave.

....................................................................................................................................................................

SHK Page 9

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

................................................................................................................................................................ [1]

(ii) State what is meant by an antinode.

....................................................................................................................................................................

................................................................................................................................................................ [1]

(iii) On Fig. 8.1, label the antinodes with the letter A. [1]

(c) A weight of 4.00 N is hung from the string in (b) and the frequency of oscillation is adjusted until a stationary wave is formed on the string. The separation of the antinodes on the string is 17.8 cm for a frequency of 125 Hz.

The speed v of waves on a string is given by the expression

where T is the tension in the string and m is its mass per unit length. Determine the mass per unit length of the string.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [5]

9. (a) Fig. 9.1 shows the variation with time t of the displacement y of a wave W as it passes a point P. The wave has intensity I.

SHK Page 10

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

Fig. 9.1A second wave X of the same frequency as wave W also passes point P. This wave has intensity I . The phase difference between the two waves is 60°.

On Fig. 9.1, sketch the variation with time t of the displacement y of wave X. [3]

(b) In a double-slit interference experiment using light of wavelength 540 nm, the separation of the slits is 0.700 mm. The fringes are viewed on a screen at a distance of 2.75 m from the double slit, as illustrated in Fig. 9.2 (not to scale).

Fig. 9.2

Calculate the separation of the fringes observed on the screen.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

SHK Page 11

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

....................................................................................................................................................................

................................................................................................................................................................ [3]

(c) State the effect, if any, on the appearance of the fringes observed on the screen when the following changes are made, separately, to the double-slit arrangement in (b).

(i) The width of each slit is increased but the separation remains constant.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [3]

(ii) The separation of the slits is increased.

....................................................................................................................................................................

....................................................................................................................................................................

....................................................................................................................................................................

................................................................................................................................................................ [2]

(1 mark of neatness) TOTAL FOR THIS PAPER: 80 MARKS

SHK Page 12

MESH INTERNATIONAL – UNIT 2 CT 3 (ALP NEW)

SHK Page 13