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Physics A-level Paper 1 > Electricity > Flashcards

Flashcards in Electricity Deck (27)
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1
Q

What is electrical current?

A

the rate of flow of charge

Q=It

2
Q

What is potential difference?

A

work done per unit charge

V=W/Q

3
Q

What is resistance?

A

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

4
Q

Explain why resistance increases with temperature in a filament bulb.

A

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

5
Q

How does potential difference change with current in a diode?

A

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

6
Q

How does a filament lamp work?

A

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

7
Q

How does current flow through a diode?

A

current can only flow in one direction

8
Q

What are the uses of a diode?

A

change AC current to DC current

protect components damaged by AC

9
Q

What does resistivity show?

A

how easily a current can flow through a given material

10
Q

How is resistivity calculated?

A

resistivity = RA/L

11
Q

How does temperature affect resistance and why?

A

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

12
Q

What is a superconductor?

A

a material with (almost) no resistance

13
Q

What condition is required for a material to superconduct?

A

very cold

14
Q

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

A

the critical temperature

15
Q

Which new materials can superconduct at higher temperatures?

A

Cuprates (copper oxides)

16
Q

What are the uses of superconductors?

A
making strong magnetic fields hence
(electromagnets)
mag-lev trains
MRI scanners
computers
improving the national grid
17
Q

How is total resistance in series calculatesd?

A

total R = R1 +R2 + … + Rn

18
Q

How is total resistance in parallel calculated?

A

1 / total R = 1/R1 + 1/R2 + … +1/Rn

19
Q

How is current shared between components in series?

A

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

20
Q

How is potential difference shared between components in series?

A

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

21
Q

How is current shared between branches in a parallel circuit?

A

total current is the sum of currents through each branch

22
Q

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

A

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

23
Q

Why are potential dividers used?

A

supply constant or variablenpotential difference from a power supply

24
Q

What are examples of potential dividers?

A

LDRs
thermistors
variable resistors

25
Q

What is a use of a potential divider?

A

audio volume control on a sound system

26
Q

What is meant by internal resistance?

A

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

27
Q

What is emf?

A

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)