Chapter 7Electricity

What is Charge?Protons have a (+) charge

Electrons have a (-) charge

Charge (q) is measured in Coulombs

The elementary charge of one (+) or (-) is 1.6 x 10-19 C

1 Coulomb = 6.25 x1018 electrons

Opposite Charges Attract

Like Charges Repel

Static Electricity

the accumulation of excess electrons on an object

CurrentThe flow of charges, usually electrons, through a wire or conductor is called electric current

Electric current is measured in amperes (A).

Potential Difference is the push that causes charges to move.

Voltage is measured in Volts (V)

ResistanceThe greater the restriction of charges to flow the lower the amount current that can flow.

Resistance is measured in ohms (Ω)

The length, diameter, and temperature of a wire influences it’s resistance.

Types of resistors:Light bulbsDoor bellsAny electrical device

Types of Currents

Direct Current (dc) is the type of electricity that we get from batteries.

In a direct current all of the electric charges move in one direction.

Types of CurrentAlternating Current (ac) is the type of electricity that we get from plugs in the wall.

In an alternating current all of the electric charges switch their direction of flow back and forth.

Ohm’s Law

V = I R

I = V / R

R = V / I

Ohm’s Law – the current in a circuit equals the voltage difference divided by the resistance.

Ohm’s Law

I = Current (Amperes)

V = Potential Difference (volts)

R = Resistance (ohms Ω)

Circuits

Total Resistance in Circuits

Series

RS = R1 + R2 + R3 + …

Total resistance increases as more

resistors are added to the series circuit

Parallel

1/RP = 1/R1 + 1/R2 +1/R3 +…

Total resistance decreases as more

resistors are added to the parallel circuit