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Physics > Electric Fields COPY > Flashcards

Electric Fields COPY Flashcards

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1
Q

Define Coulombs Law

A

The force acting between two charged bodies is inversely proportional to the square of the distance between them and is directly proportional to the product of the two charges.

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2
Q

If the distance between the charge doubles, what happens to the magnitude of the force?

A

X 1/4

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3
Q

If the distance between the charge triples, what happens to the magnitude of the force?

A

X 1/9

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4
Q

If the distance between the charge halves, what happens to the magnitude of the force?

A

X 4

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5
Q

Define electric field

A

The region of space where a charged particle feels a force

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6
Q

What is the equation for the strength of an electric field?

A

E = F/Q

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7
Q

What is the units for electric field strength?

A

N/C, V/m

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8
Q

Define electric field strength

A

The force per unit positive charge

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9
Q

What is the direction of an electric field at a point equal to?

A

The direction of the force at that point

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10
Q

Is electric field strength a scalar or vector quantity?

A

Vector

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11
Q

How does the density of an electric field line relate to its strength?

A

The density of the field lines is a measure of the strength of an electric field

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12
Q

Where does charge appear to act on a charged sphere?

A

Charge is considered to act from the centre

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13
Q

Which way do the arrows face on a field lines diagram depicting an positive charge in the centre?

A

Away from the positive centre

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14
Q

Which way do the arrows face on a field lines diagram depicting an negative charge in the centre?

A

Towards the negative centre

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15
Q

Explain what will happen to a positive particle if it is moving in the same direction as the field

A

The particle will get a force on it in the same direction and will accelerate. EQ= ma

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16
Q

Explain what will happen to a positive particle if it is moving in the opposite direction as the field

A

Force is in the opposite direction to its motion. There is a negative acceleration so the particle will slow down

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17
Q

Explain what will happen to an electron if it is moving at right angles to the field

A
  • An e- will feel a force on it in the opposite direction to the E field because it is -ve
  • The horizontal component of the e- velocity will be constant
  • The force on it causes it to accelerate in the vertical direction
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18
Q

What can be used to determine the acceleration in the vertical direction of an e- in an E field at right angle to its direction of motion

A

SUVAT equations

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19
Q

What is meant by a uniform field?

A

The force on a charge will be the same wherever the charge is between the plates

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20
Q

How do you calculate field strength between parallel plates?

A

E = V/d

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21
Q

Define electric potential

A

The electric potential at a point is defined as the work done taking a unit positive charge from infinity to that point

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22
Q

Is electric potential a scalar or vector quantity

A

Scalar

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23
Q

What is the potential around a positive charge?

A

Positive as work needs to be done. This is due the repulsive force

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24
Q

What is the potential around a negative charge?

A

Negative since the charge itself will do work to pull the charge from infinity towards itself

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25
Q

What is an equipotential?

A

Points of equal potential at right angles to the electric field lines

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26
Q

What work is done moving alone an equipotential?

A

No work is done

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27
Q

What is done moving from one potential to the other?

A

Work is done. The +ve or -ve sign relates to the direction of energy transfer

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28
Q

Is work done moving along an equipotential?

A

No

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29
Q

Is work done moving along field lines?

A

Yes

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30
Q

The work done taking a charge through a potential difference /\V is defined as:

A

W = Q /\V

31
Q

Define electrical potential energy

A

The work done in taking the charge from infinity to that point

32
Q

What does the force act on in a gravitational field?

A

Mass

33
Q

What does the force act on in a electric field?

A

A charged particle

34
Q

What is the direction of the force in a gravitational field?

A

Attractive

35
Q

What is the direction of force in an electric field?

A

Attractive/ Repulsive

36
Q

How do you calculate the field strength for a gravitational field?

A

g = F/m

37
Q

How do you calculate the field strength for an electric field?

A

E = F/q

38
Q

What is the direction of the gravitational field around an isolated object?

A

Towards object

39
Q

What is the direction of the electric field around an isolated object?

A

Towards -ve Away from +ve

40
Q

What is the definition of electrical potential?

A

The work done in taking unit positive charge from infinity to that point.

41
Q

Describe Milikan’s oil drop experiment

A
  • A charged oil drop was suspended using an electric field which opposes the weight - The charge (q) varied but was always a multiple of e
42
Q

What is the formula for Coulombs Law?

A
43
Q

Draw a diagram for the fields between two positive charges.

A
44
Q

Draw a diagram for the fields between a positive and negitive charge.

A
45
Q

Draw the path of an electron moving at right angles to the electric field.

A
46
Q

Draw the field lines for a uniform field inbetween positive and negitive plates.

A
47
Q

The electric field strength between a pair of plates 4.0cm in length in a cathode ray tube has a value of 23000N/C. An electron enters the field at right angles at a velocity of 3.7x10^7 m/s from left to right. What is the velocity and direction of the electron as it leaves the field?

A
48
Q

What is the equation that defines field strength?

A
49
Q

What does the E against r graph for a point charge in a radial field look like?

A
50
Q

What does the E against r graph for a hollow sphere of charge in a radial field look like?

A
51
Q

What does the graph of V against r graph for a radial field look like?

A
52
Q

What is the forlula for the potential, V, at a distance r form a charge Q given by?

A
53
Q

What is the equation for the potential gradient?

A
54
Q

There are two plates with a 9V potential difference. Draw in the 3V and 6V equipotential.

A
55
Q

What graph can be used to find the change in potential?

A

Graph of field strength against r

56
Q

Draw the graph of E against r for a uniform field.

A
57
Q

How do you work out the change in potential for a uniform field using an E against r graph?

A

Area under the graph

58
Q

How do you work out the change in potential for a radial field using an E against r graph?

A

Area under the graph

59
Q

What does the graph of E against r look like for a radial field?

A
60
Q

What is the derivation for E=V/d from WD moving between parallel plates?

A
61
Q
A
62
Q

What is the formula for electric potential energy?

A
63
Q

Suppose Q1 had a charge of +5C and Q2 has a charge of -3.0C, if they are 0.200m apart what is the field strength in the middle of them?

A
64
Q

Suppose Q1 had a charge of +2 microC and Q2 had a charge of +3 microC, if they are 5mm apart what is the potential difference 2mm from the 2 microC charge?

A
65
Q

Suppose Q1 had a charge of -30 microC and Q2 had a charge of +50 microC, if they are 10mm apart what is the potential difference 2mm from the -30 microC charge?

A
66
Q

What is the graph for Coulombs Law (including values for R, 2R, 3R & 4R) when the initial force is 12. What is the area under the graph equal to?

A
67
Q

What is the graph for Electric field strength (including values for R, 2R, 3R & 4R) when the initial E value is 12. What is the area under the graph equal to?

A
68
Q

What is the graph for potential (including values for R, 2R, 3R & 4R) when the initial potential is 12. What is the gradient equal to?

A
69
Q

Compare the equations for the force law between two objects for gravitational and electric fields.

A
70
Q

Compare the equations for the potential a distance r from an object if field is radial for gravitational and electric fields.

A
71
Q

Compare the equations that show how the field strength and potential are related for gravitational and electric fields.

A
72
Q

Compare the equations for the potential energy of mass/charged particle a distance r from an object if the field is radial for gravitational and electric fields.

A
73
Q

Compare the equations for the change in potential evergy of mass/charge for gravitational and electric fields.

A

Physics (15 decks)

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