[custom] 4.3 test

Question 1

Define EMF

Answer 1

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

Question 2

Define LDR

Answer 2

A light sensitive semiconductor whose resistance

increases when light intensity decreases.

Question 3

Define Ohms Law

Answer 3

For ohmic conductors kept at constant temperature, the current in the wire is directly proportional to the PD across it.

Question 4

Define PD

Answer 4

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 5

Internal Resistance

Answer 5

The resistance to the flow of charge within a source.

Internal resistance results in energy being dissipated within the source.

Question 6

Lost Volts

Answer 6

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 7

Potential Divider

Answer 7

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 8

TERMINAL PD

Answer 8

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.

Question 9

NTC Thermistor

Answer 9

Resistance decreases as temperature increases

Question 10

PTC Thermistor

Answer 10

Resistance decreases as temperature decreases

Question 11

LDR

Answer 11

Resistance decreases as light intensity increases

Question 12

Why use potential dividers?

Answer 12

To provide variable potential difference, or to provide a constant specific potential difference.

Question 13

Kirchoff’s second law

Answer 13

Sum of EMF = Sum of PD in closed loop