Electricity Y2

Question 1

How would make a direct measurement of the emf of a cell?

Answer 1

Connect voltmeter across terminals with nothing else attached

Question 2

Why do voltmeters have high resistance?

Answer 2

To ensure minimise current

Question 3

What are two possible precautions you can take in electricity experiments to ensure results reliable?

Answer 3

Turn off cell between readings, take repeats

Question 4

What defines a semiconductor?

Answer 4

Number of charge carriers increase with increase in temperature, so resistance decreases as temperature raised

Question 5

What defines a superconductor?

Answer 5

Material that has zero resistivity at and below a critical temperature

Question 6

What can often be used to define terms?

Answer 6

Formulas

Question 7

What causes resistance heating?

Answer 7

Charge carriers repeatedly colliding with the positive ions of the conducting material

Question 8

In a positive temperature coefficient thermistor, as temperature increases…

Answer 8

Resistance increases

Question 9

In a negative temperature coefficient thermistor, as temperature increases…

Answer 9

Resistance decreases

Question 10

Define emf

Answer 10

Total energy transferred when one unit of charge is moved around the circuit

Question 11

What is the gradient and y intercept equal to on a graph of pd across a cell against current flowing through it?

Answer 11

Gradient equals negative of internal resistance and y intercept equals emf