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Electric Current

What is Electricity?

• The Flow of Electrons

Closed Circuits

• Circuit – a closed,

continuous conducting

path

• Electric current – the flow

of charges (electrons)

through a wire or any

conductor

What is Voltage?

• It is the electric potential energy per

charge.

• Pushes and pulls electrons through the

circuit.

• Units: volts (v)

Voltage

• Voltage : created by a chemical cell

(battery) or generator

Chemical

Electrical Energy

Mechanical

Electrical Energy

Batteries

• Chemical reactions provide a voltage difference

between the (+) and (-) terminals

• When the terminals are connected, an electrical

current pushes through the conductor because of

the voltage difference

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Chemical Cells

• In Series

– Wired to make a battery

– Increases voltage of battery

• In Parallel

– Do not change voltage

– Makes battery last longer.

Electrical Pressure

• Charge flows from high voltage areas

to low voltage areas

• Voltage difference – the push that

causes charge to move

– Units: volts (v)

Electricity

• Battery: One terminal has extra electrons (-

charge). The other does not (+ charge)

• Pushed by (–) charges and pulled by (+)

charges

What is Electric Current?

• Flow of electrons through a conductor

• The Symbol for CURRENT is I

• Units: Amperes (A)

What is Resistance?

• Resistance – a measure of how much a material opposes the flow of electric current through it

• good conductors – lowresistance

• good insulators – highresistance

Good

Conductor

Good

Insulator

Resistance

– Units: ohms (Ω)

– Affected by four factors:

1. Material it is made of

2. Size of the conductor

– Smaller wires (conductors)

provide more resistance

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3. Length of wire

• Longer wires provide more

resistance

4. Temperature of wire

- the higher the temperature the

greater the resistance

Ohms Law

• One volt pulls one amp through one

ohm of resistance.

• Voltage = current x resistance

• V = I x R

• If R remains the same then what?

• If V remains the same then what?

Calculations using Ohm’s Law

Example #1

What is the voltage difference that flows

through a copper wire if a current of

0.75 amps is flowing through it. The

resistance of the wire is 10 Ω.

V = I * R

Control the Flow

• The flow of electrons is dependent on the voltage difference and the resistance

–The greater the voltage difference, the greater the flow

–The lower the resistance, the greater the flow

• Ohm’s Law

V = I * R

V = voltage (volts)

I = current (amps)

R = resistance (Ohms)