1. Ohm’s law

2. Learning goals
We are learning to use Ohm’s Law to solve for current, voltage and resistance.
We are learning some methods of electrical safety.

3. Ohm’s Law
Recall:
Current (A): a measure of how fast electrons are moving in a circuit.
Potential Difference / Voltage (V): a measure of the electron “pressure” in a circuit.
Higher voltage means more charged particles.
As voltage increased, current increased.
Force of repulsion became greater.

4. Ohm’s Law cont’d
Ohm’s law relates the voltage and current in a circuit to the resistance
It is given by:
we can use this to analyze behavior in parts of circuits
Where:
R = Resistance (ohms)
V = Voltage (V)
I = Current (A)
V =IR

5. GRFS
Given
Required to find
Formula
Solve

6. Example #1
A lamp has a current of 1.2 A flowing through it with a voltage of 6.0V. What is the resistance of the load?

7. Example #2
A coffee maker has a resistance of 20 Ω and a current of 5.0A when on. What is the voltage across the coffee maker?

8. Example #3
A 110 Ω resistor is connected to a power supply set at 12 V. Calculate the current going through the resistor.

9. Example #4
A toaster oven has a 24.0 Ω resistor that has 5.00 A of current going through it when the toaster is on. Calculate the potential difference across the resistor.

10. Electrical safety

11. Short circuit
accidental low-resistance connection between two points in a circuit
often causes excess current flow
connecting wires can become hot and start fire

12. Fuses & circuit breakers
fuse: safety device in an electric current that has a metallic conductor with low melting point compared to wires
current gets too high, conductor melts
circuit breaker: does same thing as fuse, but wire doesn’t melt
heats up and bends
once cooled can be reset

13. 3-prong plug third prong connects to ground wire of building
any unwanted current flow directly to ground

14. GFCI Ground Fault Circuit Interrupter
detects change in current and opens circuit
water

15. Learning goals
We are learning to use Ohm’s Law to solve for current, voltage and resistance.
We are learning some methods of electrical safety.

16. Please Complete
P570 #3,5,6,7,8