Electricity

Question 1

What is electrical current?

Answer 1

the rate of flow of charge

Q=It

Question 2

What is potential difference?

Answer 2

work done per unit charge

V=W/Q

Question 3

What is resistance?

Answer 3

How difficult it is for charge carriers to pass through a wire.
R=V/I

Question 4

Explain why resistance increases with temperature in a filament bulb.

Answer 4

the higher the temperature, the more kinetic energy the particles in the filament have, this causes them to vibrate more, causing more collisions between the charge carriers and particles in the filament, slowing the particles down

Question 5

How does potential difference change with current in a diode?

Answer 5

a tiny change in p.d can cause a huge change in current

Question 6

How does a filament lamp work?

Answer 6

a thin piece of metal wire called a filament is inside the bulb. as current passes through it its temp increases as resistance increases and it gives off light

Question 7

How does current flow through a diode?

Answer 7

current can only flow in one direction

Question 8

What are the uses of a diode?

Answer 8

change AC current to DC current

protect components damaged by AC

Question 9

What does resistivity show?

Answer 9

how easily a current can flow through a given material

Question 10

How is resistivity calculated?

Answer 10

resistivity = RA/L

Question 11

How does temperature affect resistance and why?

Answer 11

higher temp equals greater resistance
increasing temp causes particles to vibrate more, increasing the number of collisions the charge carriers make, making it more difficult for them to travel through the material

Question 12

What is a superconductor?

Answer 12

a material with (almost) no resistance

Question 13

What condition is required for a material to superconduct?

Answer 13

very cold

Question 14

What is the temperature at which a material becomes a superconductor called?

Answer 14

the critical temperature

Question 15

Which new materials can superconduct at higher temperatures?

Answer 15

Cuprates (copper oxides)

Question 16

What are the uses of superconductors?

Answer 16

making strong magnetic fields hence
(electromagnets)
mag-lev trains
MRI scanners
computers
improving the national grid

Question 17

How is total resistance in series calculatesd?

Answer 17

total R = R1 +R2 + … + Rn

Question 18

How is total resistance in parallel calculated?

Answer 18

1 / total R = 1/R1 + 1/R2 + … +1/Rn

Question 19

How is current shared between components in series?

Answer 19

the current through every component is the same as the supply current

Question 20

How is potential difference shared between components in series?

Answer 20

the total supply p.d is shared between components depending on resistance

Question 21

How is current shared between branches in a parallel circuit?

Answer 21

total current is the sum of currents through each branch

Question 22

How is potential difference shared between branches in a parallel circuit?

Answer 22

the p.d across each branch is the same as the supply p.d

Question 23

Why are potential dividers used?

Answer 23

supply constant or variablenpotential difference from a power supply

Question 24

What are examples of potential dividers?

Answer 24

LDRs
thermistors
variable resistors

Question 25

What is a use of a potential divider?

Answer 25

audio volume control on a sound system

Question 26

What is meant by internal resistance?

Answer 26

resistance within a battery, or other voltage source, that causes a drop in the source voltage when there is a current

Question 27

What is emf?

Answer 27

electromotive force
the energy which causes a current to flow through a circuit
emf = E/Q
the voltage of the battery including internal resistance,
emf = I x (R + r)