Module 1 - Electric Current, resistance and DC circuits

Question 0

One coulomb

Answer 0

Total charge supplied by a current of one ampere in a time of one second.

Question 1

Charge

Answer 1

Current x time

Question 2

Electromotive force

Answer 2

The energy transferred per unit charge when one other type of energy is converted into electrical energy.

Question 3

Potential difference

Answer 3

The electrical energy transferred per unit charge when electrical energy is converted into another form of energy.

Question 4

Ohm’s law

Answer 4

The current through a conductor is proportional to the potential difference across it, provided physical conditions such as temperature, remain constant.

Question 5

Resistivity (ohm metres)

Answer 5

Resistivity of a wire of length l, resistance R and cross-sectional area A is given by:
p = (RA/l)

Question 6

Kilo-watt hour

Answer 6

1000 watts for 3600 seconds, of 3.6MJ

Question 7

Internal resistance

Answer 7

The resistance of a battery or cell, measured in ohms.

Question 8

Insulator

Answer 8

A material with a low number density of conduction electrons, and therefore a very high resistance.

Question 9

Drift velocity

Answer 9

The average velocity of an electron as it travels through a wire due to p.d.

Question 10

Kirchhoff’s first law

Answer 10

The sum of the currents entering any junction is always equal to the sum of the currents leaving the junction (form of the conservation on energy).

Question 11

Kirchhoff’s second law

Answer 11

The sum of the e.m.f.s is equal to the sum of the p.d.s in a closed loop (a form of the conservation of energy).

Question 12

Conductor

Answer 12

A material with a high number density of conduction electrons and therefore a low resistance.

Question 13

Conservation of charge

Answer 13

Physical law stating charge is conserved in all interactions; it cannot be created or destroyed.