1. Ch. 16 - Electricity II. Electric Current Circuit Potential Difference
Resistance
Ohm’s Law

2. A. Electric Current
The flow of charges through a wire or conductor is called electric current.
Current is usually the flow of electrons.
Electric current is measured in amperes (A).
Charges flow from high voltage to low voltage.

3. A. Circuit
For charges to flow, the wire must always be connected in a closed path, or circuit.

4. C. Resistance Resistance
Resistance—the tendency for a material to oppose the flow of electrons, changing electrical energy into thermal energy and light
All materials have some electrical resistance.
Resistance is measured in ohms (Ω).
Making wires thinner, longer, or hotter increases the resistance.
Tungsten - high resistance
Copper - low resistance

5. V = I × R E. Ohm’s Law V: potential difference (V) I: current (A)
Ohm’s Law-the current in a circuit equals the voltage difference divided by the resistance
V: potential
difference (V)
I: current (A)
R: resistance ()
V = I × R
Voltage increases when current increases.
Voltage decreases when resistance increases.

6. E. Ohm’s Law R V I R = 160  I = V ÷ R V = 120 V I = (120 V) ÷ (160 )
A lightbulb with a resistance of 160  is plugged into a 120-V outlet. What is the current flowing through the bulb?
GIVEN:
R = 160 
V = 120 V
I = ?
WORK:
I = V ÷ R
I = (120 V) ÷ (160 )
I = 0.75 A I V R