charge and current

Question 1

Like charges….

Answer 1

Repel

Question 2

Unlike charges…

Answer 2

Attract

Question 3

describe net charge

Answer 3

The overall charge of an object

Question 4

state the SI unit of charge.

Answer 4

A coulomb

Question 5

what symbol represents charge?

Answer 5

Q

Question 6

what symbol represents the unit of charge?

Answer 6

C

Question 7

state the formula we can use to find the total charge of a number of particles

Answer 7

No of coulombs = Charge of 1 particle x No of particles

Question 8

Define a free charge

Answer 8

A charge which isn’t bound to an atom or molecule and can move freely

Question 9

Define number density

Answer 9

The number of free electrons per cubic metre

Question 10

Silver has a very high number density. Is it a conductor or insulator?

Answer 10

Silver has a lattice structure with positive silver ions and many free electrons per cubic metre.

As a result, silver has a very high number density, therefore its a conductor

Question 11

Diamond has a very low number density…

Answer 11

Therefore diamond is an insulator

Question 12

describe a metal’s structure

Answer 12

Metals have a lattice structure made up of positive ions and free electrons.

Question 13

why do electrons move so much in wire with no charge?

Answer 13

The delocalised electrons move due to the temperature of the wire. (even at room temperature)

Question 14

Define thermal velocity

Answer 14

The movement of free charges due to temperature

Question 15

Describe the average velocity of free charges in a wire (not connected to a power source)

Answer 15

The average velocity of the free charges in the wire is zero.

This is because the free charges move randomly.

We can assume the total charge at any point is constant

Question 16

describe why the average velocity of free charges in a wire is 0

Answer 16

Velocity is a vector quantity. The motion of free electrons due to their thermal energy is random.

on average equal numbers of electrons move in every direction.

there is no net movement of free electrons

Question 17

state the symbol that represents current

Answer 17

I

Question 18

Define current

Answer 18

The rate of flow of charge

Question 19

State the units of current

Answer 19

Ampere (A)

1 amp = 1 coulomb per second

Question 20

The number of coulombs moving past a given point per second…

Answer 20

Is called a current

Question 21

adding a power source to a circuit causes

Answer 21

The free electrons to drift towards the positive terminal

Question 22

There’s a constant amount of electrons moving…

Answer 22

Into the battery and out of the battery

Question 23

describe what happens to the electrons when a power source is connected.

Answer 23

The free electrons in the wire drift because they are pulled towards the positive terminal and pushed away from the negative terminal

Question 24

the battery dies when…

Answer 24

All the reactants are used up.

Question 25

work out the current if 3 coulombs of charge pass a point each second.

Answer 25

3 AMPS

Question 26

what is an ammeter?

Answer 26

An ammeter is a device that measures the current in a circuit

Question 27

What is an ammeter used for?

Answer 27

Ammeters are used for measing the current in a circuit

Question 28

An ideal ammeter…

Answer 28

Will not affect the current in the circuit

Question 29

State the direction of conventional current

Answer 29

Always in the opposite direction of negative charges.

Always matches the direction of the drift of positive charges