Ohm’s Law and Circuits

• describes the relationship between current, voltage, and resistance

• greater the voltage across a device with resistance, the greater the current through the device

1. Ohm’s Law

Ohm’s Law and Circuits

• current = voltage (volts)

(amps) resistance (ohms)

I = V

R• 10 amps cause wires to get

hot• 22 amps are maximum for a

house circuit• 25 or higher can start a fire

1. Ohm’s Law continued

Ohm’s Law and Circuits

You have a wire with a resistance of 5 ohms and a potential difference of 75 volts. What is the current?

R = 5 ohms V = 75 volts

I = V I = 75 volts

R 5 ohms

I = 15 amps

2. Using Ohm’s Law

Ohm’s Law and Circuits

• voltage = current x resistance

V = I x R• resistance = voltage

current

R = V

I

3. Rearranging Ohm’s Law

Ohm’s Law and Circuits

• A circuit has 3 resistors connected to a battery. A current of 1.0 A flows through the circuit. The resistance if 25 Ω. What is the voltage of the battery?

V= IR I= 1.0 A R= 25Ω

V= 1.0 A x 25Ω= 25 volts

4. Calculating Voltage

Ohm’s Law and Circuits

• measure of the stored electric charge per unit electric potential

• measured in units called farad

• capacitors store electrical energy

5. capacitance

Ohm’s Law and Circuits

• one where electrons have only one path along which they can move

• current flows from one load to next in a single path, but if one load goes out, circuit is open and won’t work

• ex. christmas tree lights

6. series circuit

Ohm’s Law and Circuits

• one where the electrons have more than one path to move along

• if load gets out, it will still work because electrons have another path to travel

7. parallel circuit

Ohm’s Law and Circuits