Unit 2.1: Conduction of electricity

Question 1

What is the unit of charge?

Answer 1

Coulomb (C)

Question 2

Particles can be___,_____ or____ charged.

Answer 2

neutral, negatively or positively

Question 3

If an object is positively charged, has it lost or gained electrons?

Answer 3

It has lost electrons

Question 4

If an object is negatively charged, has it lost or gained electrons?

Answer 4

It has gained electrons

Question 5

What is the charge of an electron in Coulombs?

Answer 5

1.6x10^-19C

Question 6

What is a conventional current?

Answer 6

When the current flows from positive to negative. This is due to conventions established a long time ago

Question 7

What is electron flow?

Answer 7

When current flows from negative to positive

Question 8

Define electric current

Answer 8

The rate of flow of charge or the flow of electrons in a circuit

Question 9

State the equation associated with electrical current

Answer 9

I=ΔQ/Δt
I=Current
Q=total charge
t=time

Question 10

On a current-time graph, what does the area under the graph give us?

Answer 10

The total charge,Q, because Q=It

Question 11

State the equation used to transfer Coulombs into electrons.

Answer 11

Q (total charge) is equivelent to
Q/e where e is 1.6x10^-19C
1C=6.25x10^18 electrons

Question 12

What is a free electron?

Answer 12

Outer electrons which are free to move around the lattice.

Question 13

If no current is flowing through a metal, how will free electrons move and what is this called?

Answer 13

They will move randomly throughout the structure. This is called Thermal velocity

Question 14

When a potential difference is applied across the ends of a metal an electric field is produced. What does this do to the free electrons?

Answer 14

The electric field exerts a force on the free
electrons, causing them to accelerate towards the highest potential (voltage).

Question 15

Explain drift velocity

Answer 15

-p.d is applied, which creates electric field
- Free electrons accelerate towards positive p.d
-bouncing from atom to atom along the way.

Question 16

State the relationship between the mean drift velocity and the applied electric field, and what this means in terms of current

Answer 16

The mean drift velocity is directly proportional to the applied field. Hence, the current we get is proportional to the applied voltage

Question 17

Why do we have to supply energy to maintain current?

Answer 17

We have to give the electrons kinetic energy to move them along.
- Lose when colliding with metal ions
-As a result, electrical energy is turned into thermal energy.

Question 18

State the equation associated with drift velocity

Answer 18

I=nAve

Question 19

Derive I=nAve

Answer 19

Area=A
Volume of wire=A x l
Number of free electrons=nAl
Total charge= Q=nale
Distance moved=x=vt
So Q=navte
It=Q
It=nAvte
I=nAvte/t
I=nAve

Question 20

What effect does doubling the drift velocity have on the current?

Answer 20

If the drift velocity doubles then the current also doubles.