Electricity & Magnetism 1

Question 1

Conductor

Answer 1

Material that permits flow of charge

Question 2

Charging by induction

Answer 2

Negatively charged rod brought near uncharged metal ball

Causes one side of ball + (closest to rod) and other -
If connect RHS with conducting wire to ground, charge will flow from ball to Earth
Disconnecting leaves + ball

Question 3

Coulomb’s law

Answer 3

F=k|q1q2|/r^2

k=1/4piE0 = 9x10^9

Question 4

Electric field

Answer 4

Force F0 that charge q0 feels at point, divided by charge
E=F0/q0

Question 5

+ q0

Answer 5

Same direction for force and E0

Question 6

-q0

Answer 6

Opposite directions for F0 and E0

Question 7

Radial vector in electric field equation

Answer 7

E=k q/r^2 r^

r^ is like i^j^k^

Question 8

Magnitude of radial vector

Answer 8

|r^|=1

Question 9

Resultant field

Answer 9

Add components

Question 10

Field lines

Answer 10

Away +
Towards -

Question 11

Work done

Answer 11

W a—>b =Fd= q0Ed

Question 12

Potential energy

Answer 12

U=k qq0/r

Or = k sum of qiqj/rij

Question 13

Electric potential

Answer 13

V=U/q0

Potential= potential energy/charge

Question 14

Inside sphere

Answer 14

No electric field

Question 15

Graph of E against r for sphere

Answer 15

Start along x axis for inside sphere
Sloping down y axis after

Question 16

Potential inside sphere

Answer 16

Same at every point inside

Question 17

Graph of v against r

Answer 17

Constant whilst inside Spencer’s then slope down y axis once outside

Question 18

Equipotential surface

Answer 18

Potential same at every point

Question 19

Equipotential lines

Answer 19

Perpendicular to field lines (meet at right angles)

Stronger E field = closer together Equipotential

Question 20

Potential gradient

Answer 20

E=- pot grad

Question 21

If E is radial

Answer 21

Er=dv/dr

Need to calculate x,y and a components of E field

Question 22

Moving charge produces

Answer 22

Magnetic field

Question 23

Second moving charge

Answer 23

Experiences magnetic force

Question 24

Unit of magnetic fields B

Answer 24

Tesla

Question 25

Particle at rest

Answer 25

No magnetic field

Question 26

Relation between F, B and v

Answer 26

F perpendicular to B and v (rh rule)

Question 27

Cross product for F

Answer 27

qVxB

VxB found using 3x3 matrix discriminant

Question 28

If both E and B

Answer 28

F=q(E+VxB)

Question 29

Magnetic field lines

Answer 29

Parallel, straight, evenly spaced= uniform magnetic field

Question 30

Into page

Answer 30

x

Question 31

Out of page

Answer 31

o

Question 32

Unit of magnetic flux

Answer 32

Webber (Wb)

Question 33

Torque

Answer 33

t=IBAsin theta

Question 34

Magnetic flux

Answer 34

I=BAcos theta

Question 35

Ampere’s law

Answer 35

Integral B.dl = u0l enclosed

Question 36

Comparing charged particles in mag filed with circular motion

Answer 36

F=|q|vB=mv^2/r

Question 37

Pitch

Answer 37

Distance travelled along x axis in 1 rotation

=2pi/w

Question 38

Magnetic moment

Answer 38

u=IA (A=area)

Anything that experiences a magnetic torque is often known as a magnetic dipole

Question 39

Maximum torque that can be obtained with same total length of wire carrying same current in same mag field

Answer 39

Max will occur when A is max
Max area when area is a circle
Calculate circumference then radius and then plug in to equation for torque