Chapter 12 - Electricity

Question 1

What is a charge carrier?

Answer 1

A charged particle e.g.electron

Question 2

What is an insulator?

Answer 2

No current passes through the substance

Question 3

What is a metallic conductor?

Answer 3

It has delocalised electrons so can carry charge

Question 4

What is a semi-conductor?

Answer 4

The number of charge carriers increases with an increase in temperature, so it does conduct electricity, but it conducts more as the heat increases

Question 5

What is potential difference?

Answer 5

The work done per unit of charge

Question 6

What is the emf?

Answer 6

The electrical energy produced per unit charge passing through the source

Question 7

What is Ohms law?

Answer 7

The pd across a metallic conductor is proportional to the current through it, provided the physical conditions don’t change

Question 8

What happens to the current in a series circuit?

Answer 8

It’s the same all the way around the circuit

Question 9

What happens to the potential difference in a series circuit?

Answer 9

It is shared amongst components

Question 10

What happens to the current in a parallel circuit?

Answer 10

It’s shared between branches

Question 11

What happens to the potential difference in a parallel circuit?

Answer 11

Each branch will have the same pd as the power source

Question 12

What is current?

Answer 12

The rate of flow of charge

Question 13

What is resistance?

Answer 13

Opposition to the current in a substance

Question 14

What is electrical power?

Answer 14

The rate, per unit time, at which electrical energy is transferred by an electric current

Question 15

What causes resistance?

Answer 15

Collisions between electrons (what flow in current) and ions (the nuclei left over after the electrons have delocalised)

Question 16

What is resistivity?

Answer 16

Resistance per unit length x area of cross section

Question 17

What is a super conductor?

Answer 17

A material that has zero electrical resistance

Question 18

What is the critical temperature?

Answer 18

The temperature at which a super conducting material’s resistivity is zero

Question 19

Uses of super conductors

Answer 19

Strong electromagnets, power cables and electronic circuits

Question 20

What happens to the current in a filament bulb when you keep upping the pd?

Answer 20

At low pd values they are pretty much directly proportional, however as the pd increases, the resistance increases - this means that there is less current at a higher pd. This is because the bulb has gotten hot and so the particles vibrate more and so the lattice vibrates, so there are more collisions with charge carriers (the resistance increases)

Question 21

What happens to the current when you up the pd in a diode?

Answer 21

The current stays at zero until 0.6V when the current starts increasing rapidly

Question 22

What happens to the resistance in a thermistor as the temperature increases?

Answer 22

As the temperature increases the resistance decreases, as more charge carriers are freed and therefore more current can flow