Republic of the Phi l ippinesDepartment of Education

Region VII , Central VisayasDivision of Mandaue City

OHM’S LAWPrepared by:

JOEMIL REY BOLAMBAOIV – Descartes

KEVIN JAY MABUTIIV – Descartes

Submitted to:

MRS. EVELYN LAURONPhysics Teacher

I. Title PageII. Table of ContentsIII. Guide CardIV. IntroductionV. Activity Card #1VI. Activity Card #2VII. Assessment Card #1VIII. Enrichment Card #1IX. Enrichment Card #2X. Answer CardsXI. Reference Card

BOOKS

Giancoli, Douglas C. (1995). Physics: Principles with Applications (4th ed ed.). London: Prentice Hall. ISBN 0-13-102153-2.

John O'Malley, Schaum's outline of theory and problems of basic circuit analysis, p.19, McGraw-Hill Professional, 1992 ISBN 0070478244

INTERNET

http://en.wikipedia.org/wiki/Ohm’s_Law

http://www.petsdo.com/blog/Origin_of_Ohm’s_Law

http://en.wikipedia.org/wiki/Resistivity

http://www.physicslab.com/Ohms%20%Law

Olah Amigos! Olah Boots! I am SIMDORA, the knowledge explorer. Today, we will be going into another fun and exciting adventure as we journey in the world of science. We will know more about the Ohm’s Law.

What is Ohm’s Law?

This Strategic Intervention Material (SIM) is designed to give you a wide understanding regarding Ohm’s Law. After going through this SIM, the reader is expected to:

Define and state the Ohm’s Law Identify the relationship of Voltage, Current and Resistance Solve problems involving the relationship of Voltage, Current and Resistance Apply Ohm’s Law in practical situations.

Now that you know what we will be encountering, here is a short review about the topic.

Olah Amigos! I heard the Boots doesn’t exactly know what Ohm’s Law. To know more about it we will be going to the house of Mr. George Simon Ohm. To get there, we must pass the brain maze, down to the Electric Castle and Then to Mr. Ohm’s House. Remember, Maze, Castle, Ohm’s House. Say it with me. Maze, Castle, Ohm’s House.....

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them.

The mathematical equation that describes this relationship is:

where I is the current through the resistance in units of amperes, V is the

potential difference measured across the resistance in units of volts, and R is

the resistance of the conductor in units of ohms. More specifically, Ohm's law

states that the R in this relation is constant, independent of the current.

The law was named after the German physicist Georg Ohm, who, in a treatise

published in 1827, described measurements of applied voltage and current

through simple electrical circuits containing various lengths of wire. He

presented a slightly more complex equation than the one above to explain

his experimental results. The above equation is the modern form of Ohm's

law.

Let’s went to Mr. George Ohm’s House. Where should we go first? Do you know where should we go first?

The Brain Maze, right. Will you help me cross the brain maze?

Thank you! Now let’s go cross the maze!

Activity 1: THE BRAIN MAZEStart

A

D G H

C I

B

E K

F L

J End

These little brain monsters won’t let you pass unless you defeat them by answering their questions. Select your answers from the answer pool.

A. The potential difference measured across the resistance.B. Who pioneered the study on the relationship of current, voltage and resistance?C. Unit of measurement for current.(D)____ states that the current through a (E)____ between two points is (F)____ proportional to the (G)_______ difference or voltage across the two points, and (H)_____ proportional to the resistance between them. I. Unit of measurement for resistance.J. The mathematical equation of the relationship of current, voltage and resistance.K. A device use to measure current.L. It is the measure of how much current can flow through a component.

Conductor

Voltage Directly

Inversely

George Ohm OhmAmpere

PotentialResistance

Ohm’s LawAmmeter

I=VR

Activity 2. The Electric Castle’s Entrance

To open the door of the Castle, we must close all its windows, but the problem is that every window may only be closed by the exact current, resistance and voltage of its circuit. Complete the table below to close the windows and open the Door of the Castle.

We’ve made it through the brain maze. Now we’re heading towards the castle. My friend told me that the castle’s door will only open if you can close all its windows. Will you help me close the windows?

The castle has 13 windows.

Window Number Voltage Current Resistance1 15 volts 30 amperes ___ ohms2 21 volts ___ amperes 3 ohms3 220 volts 20 amperes ___ ohms4 ___ volts 30 amperes 15 ohms5 110 volts ___ amperes 10 ohms6 3 volts 12 amperes ___ ohms7 ___ volts 50 amperes 25 ohms8 15 volts 30 amperes ___ ohms9 ___ volts 21 amperes 7 ohms

10 120 volts 30 amperes ___ ohms11 6 volts ___ amperes 15 ohms12 ___ volts 30 amperes 10 ohms13 ___ volts 30 amperes 5 ohms

Welcome to my Castle!

I’ve heard that you gone along an electrifying journey. Let’s see what you have learned. Here are my little playing circuits.

My friends will help me in playing with your circuits.

Activity 2. Playing With CircuitsSolve the following circuit problems. Zeus might help you in your journey.

1. An emf source of 6.0V is connected to a purely resistive lamp and a current of 2.0 amperes flows. All the wires are resistance-free. What is the resistance of the lamp?

The current flowing in a circuit containing four resistors connected in series is I = 1.0 A. The potential drops across the first, second and third resistors are, respectively: V = 5 V, V = 8 V and V = 7 V. The equivalent resistance of the circuit is R = 30

. (Hint: Resistors connected in series have the same current flows through each one.)2-5. Resistance of each resistor in the circuit R1, R2, R3 & R4

6. Voltage drop on the fourth resistor.7. Find the total voltage supplied by the battery

8-10. (3 points) In the following schematic diagram, find the total current, I.(Hint: Currents through branches of a parallel circuit add to give the total current and Voltage in each resistor is the same as the total voltage.)

Very Clever! As a reward, I’ll use my power to transport you directly inside the house of Mr. Ohm.

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere. (I) Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps. (E) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts. (R) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms. (P) Power is the amount of current times the voltage level at a given point measured in wattage or watts.

We did it! We made through the house of Mr. Ohms but it looks like he is not here so let’s just explores his place and learn more about Ohm’s Law.

The Origin of Ohm's Law

Georg Simon Ohm was born in Bavaria in 1789. His father

taught him philosophy, chemistry, mathematics and physics. In 1806 he became

a mathematics teacher in Switzerland. In 1811 he received a doctorate from

Erlangen and became a mathematics lecturer there. In 1817 he took a position as

professor of mathematics and physics at the Jesuit Gymnasium of Cologne. In

1820 he learned of Oersted's electromagnetism discovery and began

experimenting with electricity in the school's physics laboratory where he

convinced himself of what is now known as Ohm's law. In 1825 he published a

paper that explains the decrease in electromagnetic force (which is proportional

to current) around a wire as its length is increased. He published two papers in

1826 that mathematically describe electrical conduction in circuits. In 1827 he

published his famous book Die Galvanische Kette, mathematisch bearbeitet,

which contains what we now know as Ohm's law. His theories were scorned at

the time and he was forced to resign his teaching position because of them.

I am sure that your brain is going short circuit right now. Let’s relax and look back to the history of Ohm’s Law.

(Assessment)

1. An emf source of 6.0V is connected to a purely resistive lamp and a current of 2.0 amperes flows. All the wires are resistance-free. What is the resistance of the lamp?

The gain of potential energy occurs as a charge passes through the battery, that is, it gains a

potential of =6.0V. No energy is lost to the wires, since they are assumed to be resistance-

free. By conservation of energy, the potential that was gained (i.e. =V=6.0V) must be lost in the resistor. So, by Ohm's Law:

V = I R R=V/I R = 3.0

2-7. The current flowing in a circuit containing four resistors connected in series is I = 1.0 A. The potential drops across the first, second and third resistors are, respectively: V = 5 V, V = 8 V and V = 7 V. The equivalent resistance of the circuit is R = 30 .

2-5. Resistance of each resistor in the circuit R1, R2, R3 & R4

6. Voltage drop on the fourth resistor.7. Find the total voltage supplied by the battery

Hints

1. How are resistors related when connected in series? 2. What is true about potential drops of resistors when connected in series? 3. You will need to use Ohm's Law.

Solution

First, let's label the diagram with the information given in the question. There are several ways of solving this problem (see alternate solutions), but this tutorial will only go through one of these ways.

Because the resistors are connected in series, then the same current flows through each one. Using the Ohm's Law, we can find the resistances of the first, second and third resistors.

Now, using the equivalent resistance, we can find the resistance in the fourth resistor. This is a series circuit, so the equivalent resistance is the sum of the individual resistances.

The current flowing through the fourth resistor is also I=1.0A. Using Ohm's Law again, we find the voltage across this resistor.

The total voltage supplied by the battery must equal to the total voltage drop across the circuit (this is known as Kirchhoff's Voltage Law). So, we must sum up the voltage drops across the resistors.

(8-10) In the following schematic diagram, find the total current, I.

You will need Ohm's Law. 1. How are resistors related when connected in parallel? 2. What is the potential drop across each resistor? 3. How does current behave in parallel branches?

Solution We know the total potential of this circuit,

= 12.0 VSo, between points A and B, the potential must drop 12.0V. Also, the potential drop across branches of a circuit are equal. That is,

We can use Ohm's Law V = IR or I = V/R

to find the current across each resistor.

Recall that the currents through branches of a parallel circuit add to give the total current. That is, the total current 'splits up' so that part of the total current travels down each branch. Because of conservation of charge, the sum of the currents in each branch must equal the amount going into the branch. (This is Kirchhoff's Current Law.)

So, adding up the three currents, we get:

So, the total current is I = 12.0A.

Activity 2. The Electric Castle’s Entrance

To open the door of the Castle, we must close all its windows, but the problem is that every window may only be closed by the exact current, resistance and voltage of its circuit. Complete the table below to close the windows and open the Door of the Castle.

The castle has 13 windows.

Window Number Voltage Current Resistance1 15 volts 30 amperes 0.5 ohms2 21 volts 7 amperes 3 ohms3 220 volts 20 amperes 11 ohms4 450 volts 30 amperes 15 ohms5 110 volts 11 amperes 10 ohms6 3 volts 12 amperes 0.25 ohms7 6250 volts 50 amperes 25 ohms8 15 volts 30 amperes 0.5 ohms9 147 volts 21 amperes 7 ohms

10 120 volts 30 amperes 4 ohms11 6 volts 0.4 amperes 15 ohms12 300 volts 30 amperes 10 ohms13 150 volts 30 amperes 5 ohms

In completing the table above we use the following formula.

For Voltage: V = I x R

For Current: I = V / R

For Current: R = V / I

Activity 1: THE BRAIN MAZEStart

A

D G H

C I

B

E K

F L

J End

These little brain monsters won’t let you pass unless you defeat them by answering their questions. Select your answers from the answer pool.

A. Voltage is the potential difference measured across the resistance.B. George Simon Ohm pioneered the study on the relationship of current, voltage and resistance.C. Ampere is a unit of measurement for current.(D) Ohm’s Law states that the current through a (E) Conductor between two points is (F) Directly proportional to the (G) Potential difference or voltage across the two points, and (H) Inversely proportional to the resistance between them. I. Ohm is a unit of measurement for resistance.J. The mathematical equation of the relationship of current, voltage and resistance is

K. Ammeter is a device use to measure current.L. Resistance is the measure of how much current can flow through a component.