Ohmslaw power (002)

OHM’S Law Cornell Notes* Get a Textbook

Bellwork: Write the meaning of each term (IN YOUR OWN WORDS!) and write it’s unit:

VoltageCurrentResistor

Voltage, Current and ResistanceVoltage is the amount of energy per charge

moving electrons from one point to another in a circuit. It is measured in volts (v)

Current is the rate of charge flow and it is measured in amperes (A). Its unit is (I).

Resistance is the opposition of current and it is measured in ohms (W)

What is Ohm’s Law? Ohm’s law gives a relationship between the voltage (V), current (I), and resistance (R) as follows:

Example #1A 4v battery is placed in a series

circuit with a 2W resistor.

What is the total current that will flow through the circuit?

I = ?

2W4v

SolutionGiven:V = 4vR = 2 WI = ?

I = V/R = 4v/2 W I = 2A

Example#2

A 110-V battery supplies a load with a resistance of 3W,5W, and 7W respectively, what is the current in the circuit?

I = ?110v

3W

7W

5W

SolutionGiven:V= 110 vR1 = 3W R2 = 5WR3 = 7WI = ?Rtotal = R1 + R2 + R3 I = V/R

= 3 + 5 + 7 = 110/15 = 15 W = 7.33 A

How do we measure power in electric circuits?

One watt is a pretty small amount of power.

We often use kilowatts = 1000 watts

Formula of Power Power (watts)

P = VI

Voltage (volts)

Current (amps)

SolutionGiven:

V = 1.5vR = 3 W

I =V / R P = V I = 1.5 / 3 = 1.5 x 0.5 = 0.5 A = 0.75 watts

More Practice Problems

Page 841 #2-4Page 853 # 3-4

More PracticeRead Pages 829-

830Do 1-4 on page

830

SC.912.P.10.15 - investigate and explain the relationships among current, voltage, resistance, and power.

Unit Scale: 4I can generate and test ways in

which Ohm’s law can help an electrician build more energy efficient homes.

5I can explain the relationships among current, voltage, resistance, and power.

6I can compare the differences between current and voltage.

1 I can define these words using a dictionary

Agenda: Circuit Stations