Electricity

Voltage and Current

• There is a voltage across the terminals of a battery.

– cell:a device that produces an electric current by

converting chemical or radiant energy into electrical
energy

– One terminal, or end, is positive, and the other is

negative.

– Batteries convert chemical energy into electrical

energy.

​• A voltage sets charges in motion.

Electricity

Voltage and Current

• Current is the rate of charge movement.

– electric current: the rate at which charges pass

through a given point

– The SI unit of current is the ampere, A.

• 1 amp = 1 C/s

Electricity

Section 2

Voltage and Current

• In a direct current source the charges always move from

one terminal to the other in the same direction.

– example: battery

• Conventional current is the current made of positive

charge that would have the same effect as the actual
motion of charge in the material.

– The direction of current is opposite to the direction

that electrons move.

Electricity

Section 2

Electrical Resistance
〉 What causes electrical resistance?

〉 Resistance is caused by internal friction,

which slows the movement of charges
through a conducting material.

• resistance: the opposition presented to the current

by a material or device