Electric Electric CurrentCurrent

Electric Current

• The rate at which electrical The rate at which electrical charges flow through a wire charges flow through a wire or conductor is called or conductor is called electric currenelectric current.t.

Electrical current = charge passing through a given Electrical current = charge passing through a given area / timearea / time

I = I = ΔΔq/q/ΔΔtt

SI Unit = C/s = Amperes (A)SI Unit = C/s = Amperes (A)

Electric CurrentSample Problem

The current in a light bulb is 0.835 A. How long does it take for a total charge of 1.67 C to pass a point in the wire?

I = I = ΔΔq/q/ΔΔtt

ΔΔt = t = ΔΔq/Iq/I = 1.67 C / 0.835 A == 1.67 C / 0.835 A = 2.00 s2.00 s

ΔΔq = 1.67 Cq = 1.67 C I = 0.835 AI = 0.835 A

Electric Current• Charges flow from high voltage

to low voltage.

– A voltage difference is the push that causes charges to move.

– Voltage difference is measured in volts (V).

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

Electric field travels at the speed of light, but the charges do not!!!

Drift Velocity: The net velocity of a charge moving in an e- field.

Electric Current

• 2 Types:

1. Direct current (DC)

- Electrical charges move only in one direction.

- Batteries always generates a direct current (why?……fixed voltage difference).

Types of Current

Direct Current

Types of Currents (cont.) 2. Alternating current (AC)

- Electrical charges are constantly changing directions.

- Commonly used in homes and businesses throughout the world.

Why?

More efficient for long-distance electrical charge transmission.

Alternating Current

Sources of electrical current•A dry cell battery produces

a voltage difference – zinc container – carbon suspension rod– causing current to flow

between them.•Example: AA battery

Dry Cell Battery

•A wet cell battery contains two connected plates made of different metals in a conducting solution.

–Example: Car battery

Sources of electrical current (Cont.)

Generators

- Convert mechanical energy to electrical energy.

- Can produce both direct and alternating current.

Sources of electrical current (Cont.)

•Wall sockets have a voltage difference across the two holes of an electrical outlet.

– generator at a power plant provides this voltage difference.

Sources of electrical current (Cont.)