2- Chapter 16 - Charge and Field

Question 1

What is a field

Answer 1

a region of space where an appropriot entity feels a force

Question 2

V=

Answer 2

W(work)/Q(charge)

Question 3

Electrostatic field strength equation. E=

Answer 3

Force per unit charge

F/q (or V/r for uniform field)

Q/4πε₀r²

In NC^-1 or Vm^-1

^(-dV/dr)

Question 4

How is NC^-1 equivelent to Vm^-1?

Answer 4

NC^-1=NmC^-1/m=JC^-1/m=Vm^-1

Question 5

Three rules for field lines

Answer 5

1. Go from +ve to -ve
2. Dont cross
3. No kinks

Question 6

WHat do field lines do at conductors?

Answer 6

meet at a right angle

Question 7

A technique for drawing field lines

Answer 7

Use an image charge

eg if its a point charge to a planar conductor , place an image charge on the other side of the conductor.

Question 8

How to work out speed of a particle from the pd.

Answer 8

Loss of epe=QV=1/2mv²

v=(2QV/m)^0.5

Question 9

Force on a wire

Answer 9

F=BIL

Question 10

Force for a charge carrier in defelctions (a moving charge)=

Answer 10

F=BqV

Question 11

Displacement between two plates =

Answer 11

VL²/4dε

Question 12

Displacement angle tanθ in a electric field defection

Answer 12

VL/2εd

Question 13

What is a velocity selector?

Answer 13

Electric and magnetic fields combined

they remove the differening speeds of electron from the gun by making them pass thoguh slits with a magnetic field pulling it up and a electric field down

E/B=v

Question 14

Two parts of milicans oil drop experiment

Answer 14

1. See when the drop hovers ( when mg=Eq)
2. Let the drop fall at terminal velocity then mg=drag force etc.

Question 15

Force between two charges=

Answer 15

Qq/4πε₀r²

Question 16

Work done =

Answer 16

Qq/4πε₀r

Question 17

Field around a point charge=

Answer 17

Q/4πε₀r²

Question 18

Potential at a point(V)=

Answer 18

Q/4πε₀r

Question 19

Define potential?

Answer 19

The work per unit charge done in bringign a charge from infinity to the point being considered.

Question 20

What arte equpotential lines

Answer 20

Always at right angles to field lines

Lines where the potential is the same across that line.

Question 21

Electric flux(ψ)=

Answer 21

ψ = EA = Q/ε₀

Question 22

What is electric flux

Answer 22

the measure of a flow of electric field through a given area.

Question 23

E_rest=

Answer 23

mc²

Question 24

Principles of a linear accelerator

Answer 24

A series of charged electrodes

They switch between +ve and -ve at the rate an e- is being accelerated

the electrodes get longer to account for the greater speed .

Question 25

What happens if something is accelerated near c.

Answer 25

Speed wont increase but momentum and energy will

Question 26

How can accelerates be circular

Answer 26

ac current is used so that the pd switches at the right frequency

Question 27

radius of curvature of path in a magnetic field?

Answer 27

r=ρ/qB

from qvB=mv²/r

Question 28

momentum is approx … near c?

Answer 28

E/c

Question 29

What part of a field distance graph shows the potential?

Answer 29

area under it