Unit 2: Electricity

Question 1

What are both units for current?

Answer 1

A/Amps/Amperes
And
CS-1

Question 2

What is current?

Answer 2

Current is the rate of flow of charge (electrons)

Question 3

What is the unit of charge?

Answer 3

Coulombs/C

Question 4

What is the equation for current?

Answer 4

I=Q/t
Charge/time

Question 5

Derive the equation for I=nAve

Answer 5

Volume = Area*Length
n is the number of electrons per unit volume
nAl = the total number of electrons in the volume
e = the charge of 1 electron
nAle = total charge
I = total charge/time
I = nAle/t
l/t = distance/time which is also velocity, therefore
I=nAve

Question 6

What is a Coulomb

Answer 6

The unit of electrical charge

Question 7

What is potential difference?

Answer 7

Potential difference is the energy required to push 1 coulomb of charge from 1 point to another

Question 8

What does Ohm’s Law state?

Answer 8

Ohm’s Law States that potential difference across a component is directly proportional to the current through it under constant physical conditions

Question 9

How is Ohm’s law represented?

Answer 9

V=IR

Question 10

What is resistance?

Answer 10

Resistance is the measure of how difficult it is for the current to flow, a greater resistance requires a greater potential difference in order to produce a current

Question 11

How does resistance occur?

Answer 11

Resistance occurs from the collisions between free electrons and ions within the conductor.

Question 12

What does the gradient represent on an I-V graph and a V-I graph?

Answer 12

On a I-V graph the gradient represents 1/R
On a V-I graph the gradient represents R

Question 13

How does temperature affect resistance?

Answer 13

When temperature increase the ions become more energise and have more kinetic energy causing more frequent collisions with electrons leading to a greater resistance

Question 14

What is resistivity?

Answer 14

Resistivity is the measurement of a materials resistance

Question 15

What is the equation for resistivity?

Answer 15

ρ = Resistance X Area / Length

Question 16

How does a thermistor work?

Answer 16

If temperature goes down, resistance increases, if resistance increases voltage share increases.

Question 17

How do LDRs work?

Answer 17

If light levels decrease resistance increases, therefore voltage share increases.

Question 18

What is superconductivity?

Answer 18

It is when a material will conduct with 0 resistance.

Question 19

How do materials become superconductors?

Answer 19

A material will become a superconductor once cooled down to a certain temperature called the transition temperature. This can be achieved using liquid nitrogen and liquid helium.

Question 20

What are uses of superconductors?

Answer 20

Superconductors can be used to make magnets which can later be used in making floating vehicles, MRI scanners, particle accelerators

Question 21

What are potential dividers?

Answer 21

Potential dividers are circuits which deliberately divide the potential difference between 2 or more components. The PD is shared based on resistance.

Question 22

What is emf?

Answer 22

the electromotive force is the energy from a supply converted into electrical potential energy per coulomb of charge passing through it

Question 23

How is the potential difference measured using EMF giving the equation and explaining it

Answer 23

V = E - Ir

The potential difference is equal to the EMF taken away by the current multiplied by the internal resistance of the supply.