Module 4

Question 1

what is the definition of current in
* metals
* electrolytes

Answer 1

• metals: flow of electrons
• electrolytes: flow of ions

Question 2

what is the ‘number density’?

Answer 2

the number of free charge carriers per unit of volume

Question 3

what is drift velocity?

Answer 3

the average velocity of the charges moving along a conductor

not uniform journey as collides with positive metal ions

Question 4

explain the term mean drift velocity of electrons in a metal wire

Answer 4

• free electrons make collisions with metal ions to give them a random velocity
• the free electrons drift towards the positive end the supply along the wire
• the distance travelled per unit time along the length of wire is called the mean drift velocity of the electrons

Question 5

define the electro motive force

Answer 5

• measures the work done to charge carriers when they gain energy at the power supply
• energy transfered from chemical–> electrical
  ε = W/Q where ε = electromotive force (in Volts), W = work done (in Joules) and Q = charge (in Coulombs)

the output

Question 6

what is the difference between the emf and p.d?

Answer 6

• emf: charges gain energy
• pd: charges loose energy
• emf: chemical energy turns electrical
• pd: electrical energy to heat/ other forms
• emf and p.d work done by charges (Volts)

Question 7

what is ohms law?

Answer 7

which temperature of a (ohmic) comductor is constant, the current is directly proportional to the p.d

r is constant

Question 8

draw IV graph for resistor

Answer 8

Question 9

draw an IV graph for a filament light bulb

Answer 9

Question 10

draw an IV graph for a diode/LED

Answer 10

Question 12

PAG 3- techniques and procedures used to investigate elctrical charactertistics

Answer 12

Question 13

Describe the practical on how to measure the resistivity of a wire

Answer 13

Question 14

Answer 14

Question 15

how would you measure emf and terminal voltage?

Answer 15

• emf: voltmeter in parallel with battery unconnected to rest of circuit
• terminal volatge: in parallel with battery connected to rest of circuit

Question 16

how would you determine r?

Answer 16

1. record values of terminal voltage with varying current
2. plot graph
3. gradient =-r
4. y intercept = ε

Question 17

Why happens to V out as the contact is moved towards A and B?

Answer 17

As moves towards A, V out increases until = V in
As moves towards B, V in decreases until =0