Question 12
Three batteries each of 25 V having zero internal resistance are connected in series with a
resistance of 100 Ω. What would be the current in the circuit?
A. 4 A
B. 0.75 A
C. 6.5 A
D. 0.33 A
E. 0.25 A
Correct Answer: B
Explanation:
Since the batteries are connected in series, equivalent potential of batteries can be found by adding
the individual potential. Let equivalent potential be V
eq
. Therefore, V
eq
= 25 + 25 + 25
Or, V
eq
= 3 * 25 V
Or, V
eq
= 75V
Since internal resistance of the batteries is zero, only resistance to which the equivalent potential is
connected is 100 Ω. Hence, current flowing through the circuit can be found by Ohm’s law. Ohm’s law
is given as
V = IR -------------- (1)
Where
V is the potential of the cell = 75 V;
I is the current flowing through the circuit;
R is the equivalent r
esistance of the circuit = 100 Ω
Putting the values of V and R in equation 1 we get
75 = I * 100
Or, I = 75/100
Or, I = 0.75 A
Therefore, B is the correct answer option.
Question 13
Keeping the current same in a circular wire, radius is getting doubled. What will the new value
of magnetic moment be, if the initial magnetic moment is 3 × 10
-5
Am
2
?
A. 3 × 10
-5
Am
2
B. 0.75 × 10
-5
Am
2
C. 4 × 10
-5
Am
2
D. 3.2 × 10
-4
Am
2
E. 1.2 × 10
-4
Am
2
Correct Answer: E
Explanation:
Magnetic moment is given as
M = IA ------------ (1)
Where
M is the magnetic moment;
I is the current flowing in the wire;
A is the area of the circular loop;
