Energy power and resistance

Question 1

What is an ideal voltmeter?

Answer 1

Infinite resistance so no current can pass through

Question 2

Is potential difference when work is done or from charge carriers?

Answer 2

Work is done by charge carrier- they lose energy as they pass through a component.

Question 3

What is electromotive force?

Answer 3

When charge particles chain energy from a battery.

Question 4

Define resistance?

Answer 4

The ration between v and I.

Question 5

What is ohm’s law?

Answer 5

For a metallic conductor p kept at constant temperature,
Current is directly proportional to voltage.

Question 6

What is a diode?

Answer 6

Allows current to follow in one particle direction.

Question 7

How does a thermistor work?

Answer 7

Increase in temperature = decrease in resistance.
- initially the charge carriers are locked within a material and then when the temperature gets hotter the electrons are free and can move around and transfer charge.

Question 8

In dark conditions what is resistance of LDR?

Answer 8

High resistance as the number density of free electrons is low

Question 9

In light conditions what is the resistance of LDR?

Answer 9

Reistance is low and so the number density of free electrons is high.

Question 10

What is electrical energy?

Answer 10

E=pt
Measure in joules or kWh

Question 11

What is electrical power?

Answer 11

P=W/t
Measured in watts

Question 12

Define electrical power?

Answer 12

Rate of energy transfer

Question 13

Define a kilowatt hour

Answer 13

The energy transferred by and electrical device with a power of 1 kw operating for a time of 1 hour.

Question 14

Define potential difference.

Answer 14

The energy transferred from electrical energy to other forms per unit charge.

Question 15

What is 1000v equal tov

Answer 15

1000j of energy transferred per unit charge.

Question 16

What does work for potential difference?

Answer 16

Work is done by charge carriers
“Energy is transferred” by charge carriers

Question 17

What does work for emf?

Answer 17

Work is done on charge carriers
“Energy is transferred to charge carriers”

Question 18

Emf is used when charged particles…. From a power source

Answer 18

Gain energy

Question 19

Define emf

Answer 19

The energy transferred from chemical energy to electrical energy per unit charge.

Question 20

What happens when temperature of a wire increases?

Answer 20

The positive ions vibrate more and so more frequent collisions occur between the charge carriers and positive ions so the charge carriers do work more( transfer energy) more

Question 21

What is the resistivity of a good conductor?

Answer 21

Relatively low
10-8

Question 22

Why does voltmeter reading stay constant when a battery has no internal resistance?

Answer 22

Voltage isnt “lost” so the full voltage would be shown

Question 23

State a similarity of pd and emf

Answer 23

Same unit

Question 24

State difference in pd and emf:

Answer 24

Emf:
Energy is transformed to electrical
Charge gains energy
Work done on charges

Pd:
Energy is transferred to other forms eg heat
Charge loses energy
Work done by charges