1. Current and Resistance

2. Capacitor + + + + Electrons _ _ _
When a wire is connected between the plates of a capacitor the stored electrical energy is discharged in a flow of charge. This flow is extremely brief.

3. Current (I) + - Electrons
+ -
If the wire is connected to a different energy storage device (such as a dry cell) the flow of charge is sustained for a longer period of time. This sustained flow of charge is known as an electric current. The variable for current is I.
Electrons

4. Two types of Current DC – Direct current AC – Alternating current
Direct current sustains the flow of charge in one direction. Alternating current changes the direction of the flow continuously. In terms of the equations used for electricity, both types of current are usually treated the same – there is no difference between DC and AC in Ohm’s Law, for example.

5. 1 Coulomb of charge per second is 1 Ampere,
Amperes
1 Coulomb of charge per second is 1 Ampere,
or 1 Amp (A)
The Ampere was the unit of current originally, but it has been shortened to the Amp. 1C
1 A =
1 s

6. Ability of an object to limit (resist) the flow of current
Resistance (R)
Ability of an object to limit (resist) the flow of current
Conductors have low resistance while insulators have a high resistance.

7. Resistance (R) is measured in Ohms (W)

8. Ohm’s Law
V = I R
V is the potential difference or voltage, I is the current and R is the Resistance. Notice the Voltage and Current and Voltage and Resistance are directly related, where as Current and Resistance are indirectly related.

9. Light Bulb
V= 120 V
I= 2 A
R=?
The resistance is 60 ohms.

10. Speaker
V= 12 V
R= 8 W
I= ?
The current is 1.5 A