Electricity and Magnetism Answers

When a dielectric slab is placed in an external electric field, the net macroscopic (depolarising) field inside the material
is ------------------- the
external field

A positive ion passes through an electric and magnetic fields which are mutually perpendicular. The electric field strength is 20.0kV/m while the magnetic flux density is 0.40T. At what speed will the ion pass through undeflected?

6.0×104
6.0×104
m/s

5.0×104
5.0×104
m/s

7.0×104
7.0×104
m/s

An electron enters a uniform magnetic field 0.20T at an angle of
30o
30o
the field. Determine the pitch of the helical path assuming its speed is
3×107
3×107
m/s
90.6m
37.8m
56.1m
46.5m

An electric feild of 50kV/m is perpendicular to a magnetic field 0.25T. What is the velocity of a charge whose initial of motion is perpendicular to both fields and which passes through the fields undeflected?

3×103
3×103
m/s

2×105
2×105
m/s

4×107
4×107
m/s

5×104
5×104
m/s

A rectangular coil of dimensions 20cm by 15cm lies with its plane parallel to a magnetic field of
0.5W/$m2
0.5W/$m2
. The coil, carrying a current of 10A experiences a torque of 4.5Nm in the field. How many loops has the coil?
100
60
30
20

A staight wire 1.0m long carries a currernt of 100A at right-angles to a uniform magnetic field of 1.0T. Find the mechanical force on the wire and the power required to move it at 15m/s in a plane at right-angles to the field.
100N and 1.5kW
200N and 2.5kW
300N and 1.4kW
200N and 2.7kW

One end of a simple rectangular wire-loop current balance is inserted into a solenoid. A force of
3.0×10−3
3.0×10−3
N is found to act on this end when a current of 2.0A is flowing in it. If the length of the conductor forming the end of the the wire-loop is 0.
0.043T
0.26T
0.43T
0.015T

Calculate the electric field everywhere outside of a very long rod, radius R and charged to a uniform linear charge density
λ
λ
.

E⃗ =λπrϵ0r^
E→=λπrϵ0r^

E⃗ =λπϵ0ln1rr^
E→=λπϵ0ln1rr^

E⃗ =λ2πrϵ0r^
E→=λ2πrϵ0r^

E⃗ =λ2πϵ0ln1rr^
E→=λ2πϵ0ln1rr^

the electrical force on a negative charge located near an isolated positive charge
points away from the isolated charge
is tangent to a circle centred about the isolated charge
points toward the isolated charge
is zero

Calculate the potential difference between the plates of a parallel plate capacitor so that the gravitational force on a proton would be balanced by the electric field (proton mass =
1.67×10−27kg
1.67×10−27kg
, electronic charge
e=1.6×10−19C
e=1.6×10−19C
, plate separation is 0.5cm. Take
g=9.8m/s2)
g=9.8m/s2)

1.4×10−6V
1.4×10−6V

2.0×10−6V
2.0×10−6V

1.7×10−6V
1.7×10−6V

3.2×10−6V
3.2×10−6V