Electric Circuits

Question 1

Potential Difference

Answer 1

The work done per unit positive charge.

Question 2

Current

Answer 2

The rate of flow of charge.

Question 3

Ohm’s Law

Answer 3

The current through a conductor is directly proportional to the potential difference across the conductor at constant temperature.

Question 4

What is the difference between ohmic conductors and non-ohmic conductors?

Answer 4

Ohmic Conductors: Follow Ohm’s Law, have a constant resistance, and exhibit a linear voltage-current relationship. Example: metals such as copper or aluminium (resistance does not change significantly with voltage or current)

Non-Ohmic Conductors: Do not follow Ohm’s Law, have a varying resistance, and exhibit a non-linear voltage-current relationship. Example: diodes (current flows easily in one direction (with low resistance) but very little in the reverse direction (with high resistance))

Question 5

What is resistance?

Answer 5

A material’s opposition to the flow of electric charge.
(Measured in ohms)

Question 6

What is the SI unit for electrical energy?

Answer 6

Joules (J)

Question 7

What is equal to electrical power that is dissipated in a device?

Answer 7

The product of the potential difference across the device and the current flowing through it.

Question 8

What is a kilowatt hour (kWh) ?Explain.

Answer 8

The kilowatt hour (kWh) is a unit of energy.
1 kWh is the amount of energy used when 1 kilowatt (kW) o electricity is used for 1 hour.

Question 9

emf

Answer 9

The total energy supplied per coulombs of charge by the cell.

Question 10

What does emf stand for?

Answer 10

Electromotive force

Question 11

What is emf equal to?

Answer 11

The sum of the voltages across the external circuit added to the voltage across the internal resistance.
emf = Vload + Vinternal resistance
OR
end = I (Rext + r)