Electricity and Magnetism Answers

What are the dimensions of the constant k in Coulomb’s law of electrostatics?
ML2T−4T−2A−1
ML2T3A−2
M−2L3T2A−1
ML3T−4A−2

The electron beam in a television tube consists of electrons accelerated from rest through a potential difference of about 20 000V. What is the speed of the electrons? (Ignore relativistic effects). Electron rest mass is
9.11×10−31
kg and electronic charge is
1.6×10−19
C.
8.4×107
m/s
3.8×106
m/s
6×106
m/s
4.7×107
m/s

1 volt is equal to
1 watt/C
1 J/s C
1 J/C
1 N/C

Two charges
Q1=500μC
and
Q2=100μC
are located on the XY plane at the positions
r1=3j⃗
m and
r2=4i⃗
m. Find the force exerted on the
Q2
14.4i⃗ +10.8j⃗ N
14.4i⃗ –10.8j⃗ N
10.8i⃗ –14.4j⃗ N
10.8i⃗ +14.4j⃗ N

Which of the following is not true about the electric field intensity
E⃗
of a uniformly charged solid sphere?
E⃗
is maximum at the surface of the sphere
E⃗
is directly proportional to the distance from the centre of the sphere
E⃗
decreases as a square of the distance from the surface of the sphere
E⃗
decreases as a square of the distance from the centre of the sphere.

An air-cored transformer is assumed to be 100% efficient. The ratio of the secondary turns to the primary turns is 1:20. A 240V ac supply is connected to the primary coil and a
6Ω
load is connected to the secondary coil. what is the current in the primary coil?
0.10A
0.14A
2.0A
40.0A

An ac circuit consists of a voltage source
v=200sin120πt
and a
6μF
capacitor in series. Calculate the current established in the circuit
0.32A
1.24A
0.64A
2.13A

A galvanometer of resistance
120Ω
a full scale deflection with a current of 0.0005A. How would you convert it to an ammeter that reads a maximum current of 5A?
connect
2000Ω
in parallel to it
connect
200.12Ω
in series to it
connect
20.10Ω
in series to it
connect
0.012Ω
in parallel to it

A galvanometer with coil resistance
12.0Ω
shows full scale deflection for a current of 2.5mA. How would you convert it into a voltmeter of range 0 to 10.0V?

3988Ω
in series

0.43Ω
in parallel

2000Ω
in parallel

1.62Ω
in series

Which of the following does NOT affect resistance of a wire?
diameter
type of material
length
voltage