CHARGE, CURRENT AND POTENTIAL DIFFERENCE

Question 1

Define current

Answer 1

Current is the rate of flow of charge

Question 2

What is the equation to find current?

Answer 2

I=Q/T

Question 3

Define one coulomb

Answer 3

One coulomb is the amount of charge that passes a point in 1 second when the current is 1 ampere

Question 4

How would you measure current?

Answer 4

By using an ammeter

Question 5

State the elementary charge

Answer 5

1.6 x 10^-19

Question 6

What will the net charge always be on any object in terms of e.

Answer 6

a multiple of e and therefore charge is quantised

Question 7

What is potential difference?

Answer 7

It is the Work done per unit charge

Question 8

State the equation to calculate P.D.

Answer 8

V=W/Q

Question 9

Define one volt

Answer 9

One volt is when you do one joule of work moving one column of charge through the component.

Question 10

How can you measure P.D.?

Answer 10

Using a voltmeter

Question 11

What happens to the P.D. in a parallel circuit?

Answer 11

It is all the same

Question 12

State the equation to find kinetic energy?

Answer 12

eV=0.5mv^2

Question 13

Define Mean drift velocity

Answer 13

It is the average velocity of charge carriers

Question 14

What is roughly a charge carriers speed?

Answer 14

10^6

Question 15

What equation would you use if you were to find mean drift velocity?

Answer 15

I=nAve

Question 16

Complete the statement- if you double the number of electrons…..

Answer 16

the current doubles

Question 17

Complete the statement- if you double the area…..

Answer 17

the current doubles

Question 18

Complete the statement- if the electrons move twice as fast…

Answer 18

the current doubles

Question 19

In metals what happens to n (the number density of electrons)?

Answer 19

It is big n and drift velocity is small

Question 20

In semiconductors what happens to n (the number density of electrons)?

Answer 20

fewer charge carriers so drift velocity needs to be higher

Question 21

In a perfect insulator what happens to n (the number density of electrons)?

Answer 21

Have a very very small n and you would get no current

Question 22

Name a liquid that is an insulator

Answer 22

Sodium chloride

Question 23

What happens to sodium chloride once molten?

Answer 23

The liquid conducts

Question 24

What is an electrolyte?

Answer 24

A substance containing ions that conducts electricity

Question 25

How do you form a spark?

Answer 25

Gases are insulators, but if you apply a high enough voltage, electrons get ripped out of atoms giving you ions along a path.