Circuits Definitions

Question 1

Conductors

Answer 1

A material that allows the flow of electrical charge. Good conductors have a larger amount of free charge carriers to carry a current.

Question 2

Conservation of charge

Answer 2

The total charge in a system cannot change

Question 3

Conventional current

Answer 3

The flow from positive to negative terminal in a cell or battery, used to describe the current in a circuit

Question 4

Electric current

Answer 4

the rate of flow of charge

Question 5

electron flow

Answer 5

the opposite direction to conventional current flow. Electrons flow form negative to positive terminal in a cell or battery

Question 6

elementary charge

Answer 6

the smallest possible charge, equal to the charge of an electron

Question 7

insulator

Answer 7

A material that has no free charge carriers and so doesn’t allow the flow of electrical charge.

Question 8

Kirchhoff’s First Law

Answer 8

A consequence of the conservation of charge. The total

current entering a junction must equal the total current leaving it.

Question 9

Mean Drift Velocity

Answer 9

The average velocity of an electron passing through an
object. It is proportional to the current, and inversely proportional to the number of charge carriers and the cross-sectional area of the object

Question 10

Quantisation of Charge

Answer 10

The idea that charge can only exist in discrete packets

of multiples of the elementary charge.

Question 11

Semiconductors

Answer 11

A material that has the ability to change its number of charge carriers, and so its ability to conduct electricity. Light dependent resistors and thermistors are both examples.

Question 12

Diode

Answer 12

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 13

Electromotive Force

Answer 13

The energy supplied by a source per unit charge passing

through the source, measured in volts.

Question 14

Filament Lamp

Answer 14

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 15

LDR

Answer 15

A light sensitive semiconductor whose resistance

increases when light intensity decreases.

Question 16

Ohmic conductor

Answer 16

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

Question 17

Ohm’s Law

Answer 17

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 18

Potential Difference

Answer 18

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 19

Power

Answer 19

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 20

Resistance

Answer 20

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

Question 21

Resistivity

Answer 21

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 22

Conservation of Energy

Answer 22

Energy cannot be created or destroyed - it can only be

transferred into different forms.

Question 23

Internal Resistance

Answer 23

The resistance to the flow of charge within a source. Internal resistance results in energy being dissipated within the source.

Question 24

Kirchhoff’s Second Law

Answer 24

A consequence of the conservation of energy. The sum

of the voltages in any closed loop must equal zero.

Question 25

Lost Volts

Answer 25

The difference between a source’s emf and the terminal voltage. It is equal to the potential difference across the source’s internal resistance.

Question 26

Potential Divider

Answer 26

A method of splitting a potential difference, by connecting two resistors in series. The total potential difference is split in the ratio of their resistances.

Question 27

Resistors in Parallel

Answer 27

The potential difference across resistors connected in
parallel is identical for each resistor. The current is split between the resistors. The total resistance is equal to the inverse of the sum of the inverses of the resistances of the resistors.

Question 28

Resistors in Series

Answer 28

The current through resistors connected in series is identical for each resistor. The potential difference is split in the ratio of their resistances. The total resistance is equal to the sum of the resistances of the resistors.

Question 29

Terminal PD

Answer 29

The potential difference across the terminals of a power source. It is equal to the source’s emf minus any voltage drop over the source’s internal resistance