Week 1: Electricity

Question 1

What are the 4 known forces?

Answer 1

Gravitational
Electromagnetic
Weak force (Nuclear forces)
Strong force (Nuclear forces)

Question 2

Vitreous has a/an __________ of electrical fluid and is called “________”

Answer 2

An excess

Positive

Question 3

Resinous has a/an __________ of electrical fluid and is called “________”

Answer 3

A Lack of

Negative

Question 4

Heat is a form of ______________________

Answer 4

Electromagnetic radiation

Question 5

All matter possesses the fundamental quantity known as __________ and is represented by the letter __ or __ and it is a _______ quantity

Answer 5

Charge
q or Q
Scalar

Question 6

If q > 0 then it is:

Answer 6

Positive

Question 7

If q = 0 then it is:

Answer 7

Neutral

Question 8

If q

Answer 8

Negative

Question 9

Conductors allow ____________ of charge

Answer 9

High Mobility

Question 10

Semi-conductors allow ___________ of charge

Answer 10

Low Mobility

Question 11

Insulators allow ___________ of charge

Answer 11

No Mobility

Question 12

What are the 5 properties of charge?

Answer 12

1. It is Invariant - doesn’t vary
2. Net charge is conserved in any closed system
3. Charge is Quantised in lumps of e (q=ne where n=integer and e= e- charge)
4. Net charge on a body of finite extent is limited by “breakdown” or discharge
5. Charge is directly related to a fundamental force (likes repel, opposites attract)

Question 13

Net charge on a body of finite extent is limited by “breakdown” or discharge depending on:

Answer 13

• Shape and nature of the body (charge density)
• Nature and conditions of the surrounding medium (Humidity, Air, Vacuum etc)
• Proximity of the nearest conductor

Question 14

What happens when 2 insulating materials are rubbed together? What is this called?

Answer 14

1 takes a net positive charge and the other takes a net negative charge

They have areas of + and - on each surface but one polarity dominates

Charging by friction

Question 15

In air at atmospheric pressure __ per million surface atoms become charged

Answer 15

8 per million become charged

Question 16

Tribo- means:

Answer 16

Rubbing

Question 17

What is the Triboelectric series?

Answer 17

Materials at the top generally become more + when rubbed with materials beneath them.
Depends on conditions

Question 18

Even though a neutral conductor has no net charge, proximity to a second charged body causes ___________.

Answer 18

Polarisation

Question 19

What is polarisation?

Answer 19

Mobile charges rearrange in response to electromagnetic forces

Question 20

What are the 2 ways discharge occurs

Answer 20

Uniformly - Like a glow

Catastrophically - like a spark

Question 21

What is Coulombs’ law?

Answer 21

F = (kq1q2) / d^2

Where F = force, q1 and q2 = charges, k = 9 x 10^9 and d = distance between charges

Question 22

Where does charge lie on a conductor?

Answer 22

On the surface of the body

Question 23

Charge like to gather at _________

Answer 23

Pointy areas of the body

Question 24

Define the electric field:

Answer 24

F/q(test) measured in N/C (Newtons per Coulomb)

Question 25

Electric potential is:

Answer 25

V=PE/q

Where V= Voltage, PE= Potential energy and q= Charge

Question 26

How do we calculate a Voltage potential?

Answer 26

Vba = Vb - Va = ΔPE/q

Where Vb and Va = voltages