Q.1.
The resistance of carbon filament at 0°C is 104 Ω. It is connected in series to an iron wire. The temperature coefficient of resistivity of carbon and iron are -0.0003 and +0.0052/ °C respectively. What must be the resistance of iron wire so that the combined resistance does not change with temperature?
-
10%
a) 15Ω
-
20%
b) 6Ω
-
40%
c)1.5Ω
-
30%
d)156/104 Ω
Q.2.
A copper wire of length 1 metre and radius 1mm is joined in series with an iron wire of length two metres and radius 3mm and current is passed through the wire. the ratio of the current density in the copper and iron wire is [ MPPMT 1994]
-
20%
a) 18/1
-
50%
b) 9/1
-
20%
c) 6/1
-
10%
d) 2/3
Explanation
Q.3.
A ring of radius R and linear charge density λ on its surface is performing rotational motion about an axis perpendicular to its plane. If the angular velocity of the ring is ω, how much current is constituted by the ring [ GSEB]
-
12%
a)Rωλ
-
25%
b) R2ωλ
-
50%
c)Rω2λ
-
12%
d)Rωλ2
Q.4.
A cell supplies a current of 0.9A through a 2Ω resistance and current of 0.3A through a 7Ω resistor. What is the internal resistance of the cell?
-
50%
a) 1.5Ω
-
12%
b) 1.0Ω
-
38%
c)1.2Ω
-
0%
d)2.0Ω
Q.5.
The cross sectional area of the plane shown in figure is equal to 1cm2A current flows through a conductor. The current density at point P in the conductor will be ..
-
17%
a)
-
33%
b)
-
33%
c)
-
17%
d)
Q.6.
A current density of 2.5Am-2 is found to exist in conductor when an electric field of 5×10-8 Vm-1 is applied across it. The resistivity of a conductor is .. [ GSEB]
-
0%
a) 1×10-8Ωm
-
57%
b) 2× 10-8 Ωm
-
14%
c) 0.5×10-8Ωm
-
29%
d) 12.5×10-8 Ωm
Q.7.
A resistive wire is stretched till its length is increased by 100%. Due to the consequent decrease in a diameter, the change in the resistance of a stretched wire will be ... [ GSEB]
-
29%
a)300%
-
14%
b) 200%
-
29%
c)100%
-
29%
d)50%
Q.8.
At what temperature would the resistance of copper conductor be double its resistance at 0°C? Given α for copper=3.9×10-3 °C-1
-
38%
a) 256.4 °C
-
25%
b) 512.8°C
-
0%
c)100°C
-
38%
d)256.4K
Q.9.
P and Q are to points on a uniform ring of resistance R. O is the centre of the ring. If the part PQ of the ring subtends an angle θ at the centre O of the ring ( i.e. ∠POQ=θ), the equivalent resistance of the ring between the points P and Q will be .... [ Radius of ring=r and resistance per unit length of the ring=ρ] [GSEB]
-
43%
a)
-
29%
b)
-
14%
c)
-
14%
d)
Explanation
Q.10.
Figure shows a part of a closed circuit. If the current flowing through it is 2A, what will be the potential difference between point A and B
-
38%
a) +2V
-
38%
b) +1V
-
25%
c) -2V
-
0%
d) -1V
Q.11.
A voltmeter of resistance R is used to measure the potential difference across a resistance r. In which case the reading will be nearest to that in the absence of voltmeter
-
0%
a) R < r
-
50%
b) R > r
-
33%
c)R=r
-
17%
d)R=0
Q.12.
Four wires of equal length and of resistance 5Ω each are connected in the form of a square. The equivalent resistance between the diagonally opposite corners of the square is
-
20%
a) 5 Ω
-
0%
b)10 Ω
-
40%
c)20 Ω
-
40%
d)(5/4) Ω
Q.13.
The supply voltage to a room is 120V. The resistance of the lead wire is 6ohm. A 60 watt bulb is already giving light. What is the decrease in voltage across the bulb when a 240 watt heater is switched on
-
33%
a) zero volt
-
33%
b) 2.9 volt
-
33%
c) 13.3 volt
-
0%
d) 10.4 v
Explanation
Q.14.
A 60 watt incandescent lamp operates at 120V. The number of electrons passing through the filament per second
-
29%
a)1..6×1012
-
57%
b) 3.125×1018
-
0%
c)7200
-
14%
d)12.5 ×1018
Q.15.
A wire 100 cm long and 2.0 mm diameter has a resistance of 0.7Ω. The electrical resistivity of the material is
-
29%
a) 4.4 ×10-6 Ω × m
-
29%
b) 2.2 ×10-6 Ω × m
-
14%
c)1.1 ×10-6 Ω × m
-
29%
d)0.22 ×10-6 Ω × m
Q.16.
When a current I is set up in wire of radius r, the drift speed is vd. If the same current is set up through a wire of radius 2r., the drift speed will be
-
17%
a) vd /4
-
17%
b) vd /2
-
50%
c)2vd
-
17%
d)4vd
Q.17.
In a region 1019 α-particles and 1019 protons move to the left while 1019 electrons move to the right per second./ The current is
-
0%
a) 3.2 amp towards left
-
50%
b) 6.4 amp towards left
-
17%
c) 9.6 amp towards left
-
33%
d) 6.4 amp towards right
Q.18.
An electron charge (e) is revolving in a circular orbit of radius r round a nucleus of charge Ze with speed v. The equivalent current is
-
33%
a)zero
-
50%
b) ev/2πr
-
0%
c)Zev/2πr
-
17%
d)e2πr/ v
Q.19.
In absence of electric field, the mean velocity of free electrons in a conductor at absolute zero temperature T is
-
17%
a) zero
-
17%
b) independent of temperature
-
17%
c)proportional to √T
-
50%
d)proportional to T
Q.20.
Two resistance are joined in parallel whose resultant is 6/5 Ω. One of the resistance wire is broken and the effective resistance become 2&Ω. Then the resistance in ohm of the wire that got broken was
-
50%
a) 3/5
-
33%
b) 2
-
0%
c)6/5
-
17%
d)3
Q.21.
In a circuit containing two unequal resistors connected in parallel
-
17%
a) the current is same in both the resistors
-
17%
b) the current is large in larger resistor
-
50%
c) voltage drop is same across both the resistors
-
17%
d) voltage drop is larger across larger resistance
Q.22.
In an electrolyte if e denotes the charge on each type of ion and n+ and n- denote the number of positive and negative ions per unit volume and V+ and V- denotes the drift velocities of positive and negative ions, then the current density is given by
-
0%
a)en+V+
-
20%
b) en-V-
-
80%
c)en+V+ + en-V-
-
0%
d)eA[n+V+ + n-V-]
Q.23.
A certain piece of copper wire is to be shaped in to a conductor of minimum resistance. Its length and diameter should be
-
0%
a) L, D
-
50%
b) 2L, (1/2) D
-
50%
c)(1/2) L, 2D
-
0%
d)2L, 2D
Q.24.
A square aluminum rod is 1 m long and 5mm on edge. What must be the radius of another aluminum rod whose length is 1m and which has the same resistance as previous rod
-
17%
a) 5.0 mm
-
17%
b) 4.2 mm
-
67%
c) 2.8 mm
-
0%
d) 1.4 mm
Explanation
Q.25.
Certain substances lose their electrical resistance at very low temperature. These substances are called
-
17%
a) good conductors
-
0%
b) semi-conductors
-
83%
c) super conductors
-
0%
d) dielectrics
Q.26.
A wire of length 5 m and radius 1 mm has a resistance of 1 ohm. What length of wire of same material at the same temperature and of radius 2mm will also have same resistance of 1 ohm
-
17%
a)1.25 m
-
33%
b) 2.5 m
-
17%
c)10.0 m
-
33%
d)20.0 m
Q.27.
The resistance of carbon filament at 0°C is 104ohms. It is connected in series to an iron wire. The temperature coefficient of resistivity of carbon and iron are -0.0003 and +0.0052 per °C respectively. What must be the resistance of the iron wire so that the combined resistance does not change with temperature?
-
0%
a) 1.5 ohms
-
25%
b) 6 ohms
-
50%
c)1.5 ohms
-
25%
d)156/104 ohms
Q.28.
A wire has resistance 12 ohms. It is bent in the form of an equilateral triangle. The effective resistance between any two corners of triangle is
-
20%
a) 9/4 ohms
-
20%
b) 12 ohms
-
40%
c)6 ohms
-
20%
d)8/3 ohms
Q.29.
The equivalent resistance of the parallel combination is
-
40%
a) smaller than the largest resistance
-
20%
b) larger than the largest resistance
-
20%
c) smaller than the smallest resistance
-
20%
d) larger than the smallest resistance
Q.30.
Resistivity of iron is 1×10-7 ohm×metre. The resistance of the given wire of a particular thickness and length is one ohm. If the diameter and the length of wire both are doubled, the resistivity will be in in ohm ×metre
-
40%
a)1×10-7
-
20%
b) 2×10-7
-
40%
c)4×10-7
-
0%
d)8×10-7