Q.1
. The sequence of bands marked on a carbon resistor is red, red. Red silver. What is the value of
resistance?
Ans:‐ 22×102 ±10%
1
Q.2 Does the drift velocity vary with the magnitude of the current through the conductor?
Explain.
Ans. Yes. Drift velocity,
Q.3 . A wire is cut into half. What is the effect on its specific resistance?
Ans :‐ No effect.
1
Q.4 :‐ Why do we prefer a potentiometer with a longer bridge wire?
Ans:‐ When the bridge wire is longer the potential gradient is smaller. Smaller the potential
gradient more is the sensitivity of potentiometer wire.
1
Q.5 What are the factors affecting internal resistance of a cell
Ans-Nature of electrolyte
Separation between the electrode
2
Q.6 Establish a relation between the current and drift velocity
Ans‐Page 97 NCERT
2
Q.7 Describe with the help of circuit diagram how a potentiometer can be used to compare the
e.m.f. of two cells.
Ans-Potential gradient – The potential drop per unit of length of the potentiometer.
Method to compare emf of two cells –
Q.8
Define resistivity and state its SI unit. State and explain how the resistivity of a conductor varies
with temperature
Ans-Resistivity is the resistance of a conductor of that material having unit length and unit area of
cross-section.
S.I. unit = ohm metre (Ω M)
Resistivity = ↑
With increase in temperature, the electrons suffer collisions more frequently and the relaxation
time τ decreases. Hence, the resistivity of a conductor increases.
3
Q.9
(a) Three resistors 1 Ω, 2 Ω, and 3 Ω are combined in series. What is the total
resistance of the combination? (b) If the combination is connected to a battery of
emf 12 V and negligible internal resistance, obtain the potential drop across each
resistor
Ans-
(a) Three resistors of resistances 1 Ω, 2 Ω, and 3 Ω are combined in series. Total resistance of
the combination is given by the algebraic sum of individual resistances.
Total resistance = 1 + 2 + 3 = 6 Ω
(b) Current flowing through the circuit = I
Emf of the battery, E = 12 V
Total resistance of the circuit, R = 6 Ω
The relation for current using Ohm’s law is,
Potential drop across 1 Ω resistor = V1
From Ohm’s law, the value of V1 can be obtained as
V1= 2 × 1= 2 V … (i)
Potential drop across 2 Ω resistor = V 2
Again, from Ohm’s law, the value of V2 can be obtained as
V2= 2 × 2= 4 V … (ii)
Potential drop across 3 Ω resistor = V 3
Again, from Ohm’s law, the value of V3 can be obtained as
V3= 2 × 3= 6 V … (iii)
Therefore, the potential drop across 1 Ω, 2 Ω, and 3 Ω resistors are 2 V, 4 V, and 6 V
respectively.
Q.10 Derive the balance condition of Wheat Stone bridge .also draw the circuit diagram to find the
specific rsistance by meter bridge.
Ans‐
3
MULTIPLE CHOICE QUESTIONS
Circuit
Current electricity
Electron
Battery
Open circuit
Light bulb
Closed circuit
Wire
Light bulb
Battery
Wire
True
False
Light bulbs
Wire
Batteries
True
False
Light bulb
Wire
Battery
True
False
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