Electricity

Question 1

What is current?

Answer 1

The rate of flow of charge

Question 2

Where does an ammeter go and why?

Answer 2

In series due to having a negligible resistance

Question 3

What is the formula for current?

Answer 3

I = Q/t

Question 4

What is potential difference?

Answer 4

The energy transferred per coulomb of charge

Question 5

Where does a voltmeter go and why?

Answer 5

Parallel due to having a very high resistance

Question 6

What is the equation for working out voltage?

Answer 6

V=W/Q

Question 7

What is Kirchoff’s law for current in series?

Answer 7

That it is the same throughout

Question 8

What is Kirchoff’s law for current in a parallel circuit?

Answer 8

The current into the junction = the current out if the junction

Question 9

What is Kirchoff’s law for potential difference in series?

Answer 9

The sum of the P.d = The total E.M.F

Question 10

What is Kirchoff’s law for potential difference in a parallel circuit?

Answer 10

The P.d is the same across each branch

Question 11

What is Kirchoff’s law for resistance in a series circuit?

Answer 11

R1 + R2 = Rtotal

Question 12

What is Kirchoff’s law for resistance in a parallel circuit?

Answer 12

1/R1 + 1/R2 = 1/Rtotal

Question 13

What is resistivity?

Answer 13

The resistance of a 1m^2, 1m long sample of material

Question 14

What is resistivity in relation to the material?

Answer 14

It is a property

Question 15

What is the equation for resistivity?

Answer 15

R=PL/A

Question 16

What is resistivity affected by?

Answer 16

1. Cross sectional area
2. Material
3. Length
4. Temperature

Question 17

What is drift velocity?

Answer 17

The average speed particles travel along a conductor

Question 18

What is the equation for drift velocity?

Answer 18

I = nAvq

I = current 
n = charge carrier density
A = cross sectional area
v = drift velocity
q = charge

Question 19

What is resistance?

Answer 19

The degree to which a component impedes the flow of current

Question 20

How do you work out resistance?

Answer 20

R = V/I

Question 21

How do you measure resistance?

Answer 21

Using a multimeter

Question 22

What does a thermistor do?

Answer 22

A component thats resistance changes with temperature

Question 23

What does an LDR do?

Answer 23

A light dependant resistor works as light increase the resistance of the component decreases

Question 24

What is the equations for potential dividers?

Answer 24

L/L = Vout/Vsupply

Question 25

What is a positive temperature coefficient and how do they work?

Answer 25

Resistance increases as temperature rises, due to lattice ions vibrating and more electron colliding with the ions

Question 26

What is an Ntc and how does it work?

Answer 26

A negative temperature coefficient is where resistance goes down as temperature rises due to more conduction electrons being realised which allow for a higher current flow

Question 27

What is E.M.F?

Answer 27

The energy gained per coulomb of charge passing through the supply

Question 28

What is the internal resistance?

Answer 28

The resistance of the cell

Question 29

What is the terminal P.d?

Answer 29

The P.d between the cell terminals

Question 30

What are the lost volts?

Answer 30

The energy transferred per coulomb in moving through the cell

Question 31

How do you work out E.M.F?

Answer 31

``` E.M.F = Terminal P.d + Lost Volts E = V + Ir ```

Question 32

What is power?

Answer 32

Power is joules per second

Question 33

How does a fixed resistor I-V graph look?

Answer 33

Line if Y=X due to having a fixed resistance making it an ohmic conductor

Question 34

What does the I-V graph of a diode look like?

Answer 34

Flat line until a certain point on the X axis, due to a certain P.d needed for a change in current. Moreover current only flows in one direction

Question 35

What does the I-V graph of a filament bulb look like?

Answer 35

Looks like an f passing through the origin, due to as current increase, temperature increases meaning that more electron collisions occur due to lattice vibrations. Moreover it is a non-ohmic conductor