Electric Fields Flashcards

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1
Q

How do charges interact in these situations?

A
  1. Like charges repel
  2. Opposite charges attract
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2
Q

Which direction will these charges move?

A

Electric field lines shows direction of Force on +ve charges

(-ve charges are opposite)

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3
Q

How are radial and uniform electric fields different?

A
  1. Radial fields have a varying field strength (weaker when further apart)
  2. Uniform fields have a constant field strength
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4
Q

For electric fields, how are are equipotentials related to the field lines?

A

Equipotentials always perpendicular to field lines

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5
Q

How can you change this situation to increase the force on the charge?

A
  1. Increase field strength
  2. Increase magnitude of charge
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6
Q

What field lines are produced by…

a) +ve charge
b) -ve charge

A

Field lines always act…

  • Away from +ve
  • Towards -ve
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7
Q

How do the field lines look for these two interacting oppositely charged particles?

A
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8
Q

How do the field lines look for these two interacting like charged particles?

A

NOTE: Field lines never cross

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9
Q

What is the electric field strength at the following points?

A

Field strength is constant between parallel plates (capacitor)

E1 = E2 = E3

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10
Q

What is the electric potential at the following points?

A

Electric potential linearly increases between parallel plates (capacitor)

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11
Q

Define Coulomb’s Law

A
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12
Q

Define electric field strength

A

Force per unit charge acting on a small positive charge

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13
Q

What force would act on a 5C charge placed at 6NC-1?

A

F=Eq → 5x6 = 30N

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14
Q

What is wrong here?

A

Electric field strength ≠ acceleration

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15
Q

How do you calculate electric field strength outside a conducting sphere?

A

Treat it as a point charge

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16
Q

How do you calculate electric field strength inside a conducting sphere?

A

E=0 everywhere!!!

17
Q

What is the graph of electric field strength for a conducting sphere?

A
18
Q

How is electric field strength calculated here?

A

For parallel plates calculate E first if possible

19
Q

How do you work out the resultant field strength between charges?

A
  1. Work out field strength from each
  2. Label vectors
  3. Add or subtract field strengths
20
Q

Can you use SUVATs here?

A

Yes!

Field strength constant → Acceleration constant

21
Q

Why is potential energy here +ve?

A

Ep = 0 at

Increases as charge moves closer

22
Q

Why is potential energy here +ve?

A

Ep = 0 at

Increases as charge moves closer

23
Q

Why is potential energy here -ve?

A

Ep = 0 at

Decreases as charge moves closer

24
Q

Why is potential energy here -ve?

A

Ep = 0 at

Decreases as charge moves closer

25
Q

Define electric potential

A

Work done per coulomb moving positive charge from infinity to that point

26
Q

Why does the moving charge’s potential energy increase?

A

Equipotentials show the change in potential of a +ve charge

If +ve charge → decreases

If -ve charge → increases

27
Q

How are these charges different?

A

Q is the charge creating the field

q is the charge moving in the field

28
Q

What is wrong here?

A

Electric potential is scalar

But they are opposite → must be subtracted

29
Q

How do you calculate the neutral electric field strength (or force) point between charges?

A
30
Q

How do you calculate the neutral electric potential point between charges?

A
31
Q

What is the graph of electric force for a conducting sphere?

A

Same as field strength graph

32
Q

What is the graph of electric potential for a positively charged conducting sphere?

A
33
Q

What is the graph of electric potential for a negatively charged conducting sphere?

A
34
Q

What two situations produce a uniform electric field?

A
  1. Radial field over a short distance
  2. Field between 2 parallel plates