9.Energy, Power and Resistance

Question 1

Diode

Answer 1

A component that allows current through in one direction only. In the correct direction, diodes have a threshold voltage (typically 0.6 V) above which current can flow.

Question 2

Electromotive Force

Answer 2

The energy supplied by a source per unit charge passing through the source, measured in volts.

Question 3

Filament Lamp

Answer 3

A bulb consisting of a metal filament, that heats up and glows to produce light. As the filament increases in temperature, its resistance increases since the metal ions vibrate more and make it harder for the charge carriers to pass through.

Question 4

I-V Characteristics

Answer 4

Plots of current against voltage, that show how different components behave.

Question 5

Kilowatt-Hour

Answer 5

A unit of electrical energy. It is usually used to measure domestic power consumption.

Question 6

Light-Dependent Resistor

Answer 6

A light sensitive semiconductor whose resistance increases when light intensity decreases.

Question 7

Ohm

Answer 7

The unit of resistance

Question 8

Ohmic Conductor

Answer 8

A conductor for which the current flow is directly proportional to the potential difference across it, when under constant physical conditions.

Question 9

Ohm’s Law

Answer 9

The current and potential difference through an ohmic conductor held under constant physical conditions are directly proportional, with the constant of proportionality being resistance.

Question 10

Potential Difference

Answer 10

The difference in electrical potential between two points in a circuit. It is also the work done per coulomb to move a charge from the lower
potential point to the higher potential point. It is measured in Volts.

Question 11

Power

Answer 11

The rate of energy transfer in a circuit. It can be calculated as the product of the current and the potential difference between two points. It is measured in
Watts.

Question 12

Resistance

Answer 12

A measure of how difficult it is for current to flow through a material.

Question 13

Resistivity

Answer 13

A measure of how difficult it is for charge to travel through a material. It is proportional to the object’s resistance and cross-sectional area, and inversely proportional to the object’s length. It is measured in Ohm metres.

Question 14

Resistor

Answer 14

A device that has a fixed resistance and follows Ohm’s law.

Question 15

Volt

Answer 15

The unit of potential difference.