Electric Circuits Answers

A cirrent flows in a wire of circular cross-section with the free electrons travelling with a mean drift velocity v. If an equal current flows in a wire of the same material but of twice theradius, what is the new mean drift velocity?
v/4
v/2
2v
4v

A wire with resistance of
8.0Ω
8.0Ω
is drawn out through a die so that its new length is three times its original length. Find the resistance of the longer wire assuming that the resistivity and density of the material are unaffected by the drawing process.

72Ω
72Ω

60Ω
60Ω

80Ω
80Ω

45Ω
45Ω

Calculate the resistance of 180 m of silver wire having a cross section of
0.33mm2
0.33mm2
. The resistivity of silver is
1.6×10−8Ωm
1.6×10−8Ωm

11.2Ω
11.2Ω

9.6Ω
9.6Ω

14.6Ω
14.6Ω

7.5Ω
7.5Ω

A 0.40 mm diameter copper wire carries a current of
3μA
3μA
. Find the current density in the wire

15.16A/m2
15.16A/m2

33.32A/m2
33.32A/m2

26.17A/m2
26.17A/m2

23.87A/m2
23.87A/m2

The average velocity of the electrons in a piece of wire of cross-sectional area
2.0×10−6m2
2.0×10−6m2
is
2.5×10−4m/s
2.5×10−4m/s
when a steady current of 4.0 A is flowing. Calculate the number of free electrons per unit volume of the material

3×1019
3×1019

5×1020
5×1020

2×1023
2×1023

5×1028
5×1028

A galvanometer of resistance
120Ω
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
2000Ω
in parallel to it
connect
200.12Ω
200.12Ω
in series to it
connect
20.10Ω
20.10Ω
in series to it
connect
0.012Ω
0.012Ω
in parallel to it

The following are true about electric field lines except that they
are drawn such that the magnitude of the field is proportional to the number of lines crossing a unit area perpendicular to the lines
do not intersect one another
are discontinuous and may terminate in a vacuum
give the direction of motion of a unit positive test-charge under the action of the electrostatic force

7 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

A tiny ball of mass 0.60 g is suspended from a rigid support with a piece of thread in a horizontal electric field of intensity 700 N/C. The ball is in equilibrium when the thread is inclined at an angle of
20o
to the vertical. What are the magnitude and sign of the charge on the ball? Take
g=9.8m/s2
−3.1×10−6C
3.2×10−6C
4.2×10−6C
−4.1×10−3

A huge spark due to electric discharge in the atmosphere produces all of the following except
A Lightning
B Rapid expansion of surrounding air
C shock waves
D gamma radiation.