Current Electricity Practice Questions - DPP for JEE

 Page 1


PART-I (Single Correct MCQs)
1. Two sources of equal emf are connected to an external resistance R.
The internal resistance of the two sources are R
1
and R
2 
(R
1 
> R
1
). If the
potential difference across the source having internal resistance  is
zero, then
(a) R = 
(b) R = 
(c) R = 
(d) R = 
2. The total current supplied to the circuit by the
battery is
(a) 4 A
(b) 2 A
(c) 1 A
Page 2


PART-I (Single Correct MCQs)
1. Two sources of equal emf are connected to an external resistance R.
The internal resistance of the two sources are R
1
and R
2 
(R
1 
> R
1
). If the
potential difference across the source having internal resistance  is
zero, then
(a) R = 
(b) R = 
(c) R = 
(d) R = 
2. The total current supplied to the circuit by the
battery is
(a) 4 A
(b) 2 A
(c) 1 A
(d) 6 A
3. To get maximum current in a resistance of 3 ohms, one can use n rows
of m cells (connected in series) connected in parallel. If the total
number of cells is 24 and the internal resistance of a cell is 0.5 ohms
then
(a) m = 12, n = 2
(b) m = 8, n = 3
(c) m = 2, n = 12
(d) m = 6, n = 4
4. See the electric circuit shown in the figure.
Which of the following equations is a correct
equation for it?
(a) e
2
 – i
2
  r
2
 – e
1
 –  i
1
  r
1
 = 0
(b) - e
2
 – (i
1
 + i
2
) R+ i
2
  r
2
 = 0
(c) e
1
 – (i
1
 + i
2
) R +  i
1
  r
1
 = 0
(d) e
1
 – (i
1
 + i
2
) R– i
1
  r
1
 = 0
5. In a neon gas discharge tube Ne
+
 ions moving through a cross-section
of the tube each second to the right is 2.9 × 10
18
, while 1.2 × 10
18
electrons move towards left in the same time; the electronic charge
being 1.6 × 10
–19
 C, the net electric current is
(a) 0.27 A to the right
(b) 0.66 A to the right
(c) 0.66 A to the left
(d) zero
6. Variation of current passing through a conductor
as the voltage applied across its ends is varied as
shown in the adjoining diagram. If the resistance
(R) is determined at the points A, B, C and D, we
will find that
Page 3


PART-I (Single Correct MCQs)
1. Two sources of equal emf are connected to an external resistance R.
The internal resistance of the two sources are R
1
and R
2 
(R
1 
> R
1
). If the
potential difference across the source having internal resistance  is
zero, then
(a) R = 
(b) R = 
(c) R = 
(d) R = 
2. The total current supplied to the circuit by the
battery is
(a) 4 A
(b) 2 A
(c) 1 A
(d) 6 A
3. To get maximum current in a resistance of 3 ohms, one can use n rows
of m cells (connected in series) connected in parallel. If the total
number of cells is 24 and the internal resistance of a cell is 0.5 ohms
then
(a) m = 12, n = 2
(b) m = 8, n = 3
(c) m = 2, n = 12
(d) m = 6, n = 4
4. See the electric circuit shown in the figure.
Which of the following equations is a correct
equation for it?
(a) e
2
 – i
2
  r
2
 – e
1
 –  i
1
  r
1
 = 0
(b) - e
2
 – (i
1
 + i
2
) R+ i
2
  r
2
 = 0
(c) e
1
 – (i
1
 + i
2
) R +  i
1
  r
1
 = 0
(d) e
1
 – (i
1
 + i
2
) R– i
1
  r
1
 = 0
5. In a neon gas discharge tube Ne
+
 ions moving through a cross-section
of the tube each second to the right is 2.9 × 10
18
, while 1.2 × 10
18
electrons move towards left in the same time; the electronic charge
being 1.6 × 10
–19
 C, the net electric current is
(a) 0.27 A to the right
(b) 0.66 A to the right
(c) 0.66 A to the left
(d) zero
6. Variation of current passing through a conductor
as the voltage applied across its ends is varied as
shown in the adjoining diagram. If the resistance
(R) is determined at the points A, B, C and D, we
will find that
(a) R
C
 = R
D
(b) R
B
 > R
A
(c) R
C
 > R
B
(d) R
A
 > R
B
7. Twelve resistors each of resistance 16 are
connected in the circuit as shown. The net
resistance between AB is
(a) 1
(b) 2
(c) 3
(d) 4
8. The masses of the three wires of copper are in the ratio of 1 : 3 : 5 and
their lengths are  in the ratio of 5 : 3 : 1. The ratio of their electrical
resistance is
(a) 1 : 3 : 5
(b) 5 : 3 : 1
(c) 1 : 25 : 125
(d) 125 : 25 : 1
9. A cylindrical solid of length L and radius a is having varying resistivity
given by ? = ?
0
x, where ?
0
 is a positive constant and x is measured from
left end of solid. The cell shown in the figure is having emf V and
negligible internal resistance. The electric field as a function of x is best
described by
Page 4


PART-I (Single Correct MCQs)
1. Two sources of equal emf are connected to an external resistance R.
The internal resistance of the two sources are R
1
and R
2 
(R
1 
> R
1
). If the
potential difference across the source having internal resistance  is
zero, then
(a) R = 
(b) R = 
(c) R = 
(d) R = 
2. The total current supplied to the circuit by the
battery is
(a) 4 A
(b) 2 A
(c) 1 A
(d) 6 A
3. To get maximum current in a resistance of 3 ohms, one can use n rows
of m cells (connected in series) connected in parallel. If the total
number of cells is 24 and the internal resistance of a cell is 0.5 ohms
then
(a) m = 12, n = 2
(b) m = 8, n = 3
(c) m = 2, n = 12
(d) m = 6, n = 4
4. See the electric circuit shown in the figure.
Which of the following equations is a correct
equation for it?
(a) e
2
 – i
2
  r
2
 – e
1
 –  i
1
  r
1
 = 0
(b) - e
2
 – (i
1
 + i
2
) R+ i
2
  r
2
 = 0
(c) e
1
 – (i
1
 + i
2
) R +  i
1
  r
1
 = 0
(d) e
1
 – (i
1
 + i
2
) R– i
1
  r
1
 = 0
5. In a neon gas discharge tube Ne
+
 ions moving through a cross-section
of the tube each second to the right is 2.9 × 10
18
, while 1.2 × 10
18
electrons move towards left in the same time; the electronic charge
being 1.6 × 10
–19
 C, the net electric current is
(a) 0.27 A to the right
(b) 0.66 A to the right
(c) 0.66 A to the left
(d) zero
6. Variation of current passing through a conductor
as the voltage applied across its ends is varied as
shown in the adjoining diagram. If the resistance
(R) is determined at the points A, B, C and D, we
will find that
(a) R
C
 = R
D
(b) R
B
 > R
A
(c) R
C
 > R
B
(d) R
A
 > R
B
7. Twelve resistors each of resistance 16 are
connected in the circuit as shown. The net
resistance between AB is
(a) 1
(b) 2
(c) 3
(d) 4
8. The masses of the three wires of copper are in the ratio of 1 : 3 : 5 and
their lengths are  in the ratio of 5 : 3 : 1. The ratio of their electrical
resistance is
(a) 1 : 3 : 5
(b) 5 : 3 : 1
(c) 1 : 25 : 125
(d) 125 : 25 : 1
9. A cylindrical solid of length L and radius a is having varying resistivity
given by ? = ?
0
x, where ?
0
 is a positive constant and x is measured from
left end of solid. The cell shown in the figure is having emf V and
negligible internal resistance. The electric field as a function of x is best
described by
(a)
(b)
(c)
(d) None of these
10. All batteries are having emf 10 volt and internal resistance negligible.
All resistors are in ohms. Calculate the current in the right most 2?
resistor.
(a)
(b)
(c)
(d)
11. n equal resistors are first connected in series and then connected in
parallel. What is the ratio of the maximum to the minimum resistance ?
(a) n
(b) 1/n
2
(c) n
2
(d) 1/ n
Page 5


PART-I (Single Correct MCQs)
1. Two sources of equal emf are connected to an external resistance R.
The internal resistance of the two sources are R
1
and R
2 
(R
1 
> R
1
). If the
potential difference across the source having internal resistance  is
zero, then
(a) R = 
(b) R = 
(c) R = 
(d) R = 
2. The total current supplied to the circuit by the
battery is
(a) 4 A
(b) 2 A
(c) 1 A
(d) 6 A
3. To get maximum current in a resistance of 3 ohms, one can use n rows
of m cells (connected in series) connected in parallel. If the total
number of cells is 24 and the internal resistance of a cell is 0.5 ohms
then
(a) m = 12, n = 2
(b) m = 8, n = 3
(c) m = 2, n = 12
(d) m = 6, n = 4
4. See the electric circuit shown in the figure.
Which of the following equations is a correct
equation for it?
(a) e
2
 – i
2
  r
2
 – e
1
 –  i
1
  r
1
 = 0
(b) - e
2
 – (i
1
 + i
2
) R+ i
2
  r
2
 = 0
(c) e
1
 – (i
1
 + i
2
) R +  i
1
  r
1
 = 0
(d) e
1
 – (i
1
 + i
2
) R– i
1
  r
1
 = 0
5. In a neon gas discharge tube Ne
+
 ions moving through a cross-section
of the tube each second to the right is 2.9 × 10
18
, while 1.2 × 10
18
electrons move towards left in the same time; the electronic charge
being 1.6 × 10
–19
 C, the net electric current is
(a) 0.27 A to the right
(b) 0.66 A to the right
(c) 0.66 A to the left
(d) zero
6. Variation of current passing through a conductor
as the voltage applied across its ends is varied as
shown in the adjoining diagram. If the resistance
(R) is determined at the points A, B, C and D, we
will find that
(a) R
C
 = R
D
(b) R
B
 > R
A
(c) R
C
 > R
B
(d) R
A
 > R
B
7. Twelve resistors each of resistance 16 are
connected in the circuit as shown. The net
resistance between AB is
(a) 1
(b) 2
(c) 3
(d) 4
8. The masses of the three wires of copper are in the ratio of 1 : 3 : 5 and
their lengths are  in the ratio of 5 : 3 : 1. The ratio of their electrical
resistance is
(a) 1 : 3 : 5
(b) 5 : 3 : 1
(c) 1 : 25 : 125
(d) 125 : 25 : 1
9. A cylindrical solid of length L and radius a is having varying resistivity
given by ? = ?
0
x, where ?
0
 is a positive constant and x is measured from
left end of solid. The cell shown in the figure is having emf V and
negligible internal resistance. The electric field as a function of x is best
described by
(a)
(b)
(c)
(d) None of these
10. All batteries are having emf 10 volt and internal resistance negligible.
All resistors are in ohms. Calculate the current in the right most 2?
resistor.
(a)
(b)
(c)
(d)
11. n equal resistors are first connected in series and then connected in
parallel. What is the ratio of the maximum to the minimum resistance ?
(a) n
(b) 1/n
2
(c) n
2
(d) 1/ n
12. There is an infinite wire grid with cells in the form of equilateral
triangles. The resistance of each wire between neighbouring joint
connections is R
0
. The net resistance of the whole grid between the
points A and B as shown is
(a) R
0
(b)
(c)
(d)
13. You are given a resistance coil and a battery. In which of the following
cases is largest amount of heat generated ?
(a) When the coil is connected to the battery directly
(b) When the coil is divided into two equal parts and both the parts are
connected to the battery in parallel
(c) When the coil is divided into four equal parts and all the four parts are
connected to the battery in parallel
(d) When only half the coil is connected to the battery
14. A potentiometer circuit is set up as shown.
The potential gradient, across the
potentiometer wire, is k volt/cm and the
ammeter, present in the circuit, reads 1.0 A
when two way key is switched off. The
balance points, when the key between the
terminals (i) 1 and 2 (ii) 1 and 3, is plugged 
in, are found to be at lengths l
1
 cm and l
2
 cm
respectively. The magnitudes, of the resistors