Electrical Physics

Question 1

Like charges…

Answer 1

Repel

Question 2

Unlike charges

Answer 2

Attract

Question 3

Can charge be created or destroyed?

Answer 3

No, it is only ever transfered from one object to another.

Question 4

What does an electrostatic charge involve?

Answer 4

An imbalance of positive and negative charges.

Question 5

Are the charges on a proton and electron equal?

Answer 5

Yes, they are however opposite in sign.

Question 6

What happens when a charged object is placed near a conductor?

Answer 6

An opposite charge will be induced on the side of the conductor nearer the charge and a like charge on the side further away from the charge.

Question 7

Coulumbs law for the force between two charges q1 and q2 at a distance of r is :

Answer 7

F=kq1q2/r2(squared)

Question 8

The electric field E in any region of space is the ecectric force per unit of charge in that space. The equation is…

Answer 8

E=F/q

Question 9

The force on acharge q in an electric field is given by…

Answer 9

F=qE

Question 10

What does a battery establish is a conductor connected to its terminals?

Answer 10

An electric field.

Question 11

What is the direction of an electric current?

Answer 11

The direction of transfer of the positive charge.

Question 12

What does a source of EMF give charges?

Answer 12

Electrical potential energy

Question 13

What is a potential diference?

Answer 13

The loss of potential energy per unit charge as charge flows through a circuit element.

Question 14

What equation is used for energy lost?

Answer 14

E=qV

Question 15

What does the current-potential difference relationship for an electrical device describe?

Answer 15

The electrical behaviour of the device.

Question 16

What is matter made up of?

Answer 16

Vast numbers of positive and negative charges (protons and neutrons)

Question 17

What does the current-potential difference relationship for an electrical device describe?

Answer 17

The electrical behaviour of the device.

Question 18

What is Ohm law?

Answer 18

The cureent is directly proportional to the voltage.

Question 19

What is a device with a linear I-V graph known as?

Answer 19

An ohmic conductor. It obeys Ohm law

Question 20

Is the current in an non-ohmic conductor directly proportional to the voltage that is is dependant on?

Answer 20

No

Question 21

What is the resistance of a conductor defined as?

Answer 21

The ratio of the potential difference to the current, thus V=IR.

Question 22

Is the resistance of a ohmic conductor constant?

Answer 22

Yes

Question 23

How does the current flow in a metal?

Answer 23

Because of the potential difference along it.

Question 24

What does the amount of current that can flow through a material depend on?

Answer 24

The field, the cross sectional area and the length as well as the nature and temperature of the material.

Question 25

What is the resitance of a conductor given by?

Answer 25

R=pL/A where p is resistivity

Question 26

What can potential energy stored when charge is concentrated be converted to?

Answer 26

Other forms of energy or in man made devices.

Question 27

The rate at which energy is releasesd is given by?

Answer 27

The product of the potential (voltage) and the current P=VI. In SI units 1 watt is equal to 1 volt x 1 ampere 1W=1AV

Question 28

Total energy produced is given by?

Answer 28

E=Pt

Question 29

What is the direction of an EMF?

Answer 29

It can be constant which gives rise to a direct current DC. | Or it can be alternating which gives rise to alternating current AC.

Question 30

Why is power transmitted to cities at a high voltage?

Answer 30

In order to keep the current needed relatively low.

Question 31

What does an electric circuit normally consist of?

Answer 31

A source of EMF, conductors to carry current with little loss of energy, and circuit elements which turns the potential energy of the charges into some form of useful energy.

Question 32

In any electrical circuit the sum of all the currents flowing into any point is equal to?

Answer 32

The sum of the currents flowing out of it.

Question 33

The sum of all EMF values around a circuit is equal to?

Answer 33

The sum of all potential drops around the circuit.

Question 34

All circuits are combinations of?

Answer 34

Circuit elements in series or in parallel.

Question 35

In a simple series circuit the total voltage drop is the sum of?

Answer 35

The individual drops.

Question 36

In a simple parallel circuit the same voltage drop occurs across both elements. The total current that flows is the sum of?

Answer 36

The two individual currents.

Question 37

How does a source of EMF create electrical potential energy?

Answer 37

It uses some form of energy. Batteries use chemical energy. Generators use mechanical energy.

Question 38

If several sources of EMF are combined in series, the total EMF will be given by the sum of?

Answer 38

The individual sources.

Question 39

Sources of EMF should only be combined in parallel if?

Answer 39

They provide the same voltage. Cells in such a battery only need to provide half the current they would otherwise.