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NCERT Solutions for class 12 Physics | Chapter 3 - Current Electricity

Questions
1 In a potentiometer of 10 wires, the balance point is obtained on the 7th wire. To shift the balance point to 9th wire, we should
A decrease resistance in the main circuit.
B increase resistance in the main circuit.
C decrease resistance in series with the cell whose emf is to be measured.
D increase resistance in series with the cell whose emf is to be determined.

Answer:increase resistance in series with the cell whose emf is to be determined.
2 In parallel combination of n cells, we obtain
A more voltage
B more current
C less voltage
D less current

Answer:more current
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3 In the series combination of two or more than two resistances
A the current through each resistance is same.
B the voltage through each resistance is same.
C neither current nor voltage through each re-sistance is same.
D both current and voltage through each resis¬tance are same.

Answer:the current through each resistance is same.
4 A charge is moving across a junction, then
A momentum will be conserved.
B momentum will not be conserved.
C at some places momenturii will be conserved and at some other places momentum will not be conserved.
D none of these.

Answer:none of these.
5 In a Wheatstone bridge if the battery and galvanometer are interchanged then the deflection in galvanometer will
A change in previous direction
B not change
C change in opposite direction
D none of these.

Answer:not change
6 When a metal conductor connected to left gap of a meter bridge is heated, the balancing point
A shifts towards right
B shifts towards left
C remains unchanged
D remains at zero

Answer:shifts towards right
7 An electric heater is connected to the voltage supply. After few seconds, current gets its steady value then its initial current will be
A equal to its steady current
B slightly higher than its steady current
C slightly less than its steady current
D zero

Answer:slightly higher than its steady current
8 The I-V characteristics shown in figure represents

Class 12 Physics Chapter 3 Current Electricity

A ohmic conductors
B non-ohmic conductors
C insulators
D superconductors

Answer:non-ohmic conductors
9 AB is a wire of potentiometer with the increase in the value of resistance R, the shift in the balance point J will be

Class 12 Physics Chapter 3 Current Electricity

A towards B
B towards A
C remains constant
D first towards B then back towards A.

Answer:towards B
10 Combine three resistors 5 Q, 4.5 Q and 3 Q in such a way that the total resistance of this combination is maximum
A 12.5 Q
B 13.5 Q
C 14.5 Q
D 16.5 Q

Answer:12.5 Q
11 The resistivity of alloy manganin is
A Nearly independent of temperature
B Increases rapidly with increase in temperature
C Decreases with increase in temperature
D Increases rapidly with decrease in temperature

Answer:Nearly independent of temperature
12 If n cells each of emf e and internal resistance r are connected in parallel, then the total emf and internal resistance will be
A Class 12 Physics Chapter 3 Current Electricity
B ε,nr
C Class 12 Physics Chapter 3 Current Electricity
D nε, nr

Answer:Class 12 Physics Chapter 3 Current Electricity
13 A cell having an emf E and internal resistance r is connected across a variable external resistance R. As the resistance R is increased, the plot of potential difference V across R is given by
A Class 12 Physics Chapter 3 Current Electricity
B Class 12 Physics Chapter 3 Current Electricity
C Class 12 Physics Chapter 3 Current Electricity
D Class 12 Physics Chapter 3 Current Electricity

Answer:Class 12 Physics Chapter 3 Current Electricity
14 Thermo electricity was discovered by:
A Joule
B Peitier
C Thomson
D Seebeck

Answer:Seebeck
15 When the wires are connected in parallel, the heat produced in the thinner wire is H1 and that in the thicker wire is H2 Then:
A H1 = H2
B H1 < H2
C H1 > H2
D H1 ≥ H2

Answer:H1 < H2
16 A wire P is half the diameter and half the length of a wire Q of similar material. The ratio of resistances of P to that 0 is:
A 4 : 1
B 8 : 1
C 2 : 1
D 1 : 2

Answer:2 : 1
17 In a Wheatstone bridge, the resistance each arm is 10 Ω. If the resistance galvanometers is also 10 Ω, then effective resistance of the bridge will be :
A 40 Ω
B 20 Ω
C 10 Ω
D 5 Ω

Answer:10 Ω
18 Two bulbs 25 W, 220 V and 100 W, 220 V are given. Which has higher resistance?
A 25 W
B 100 W
C both bulbs have equal resistance
D resistance of bulbs can not be compared

Answer:25 W
19 In India electricity is supplied fordomestic use at 220 V. It is supplied at 110 V in U.S.A. If the resistance of a 60 W bulb use in India is R. the resistance of a 60 W bulb for use in USA will be:
A 2 R
B R
C R/2
D R/4

Answer:R/4
20 Which of the following has a negative temperature coefficient of resistance ?
A Tungsten
B Carbon
C Nichrome
D Platinum

Answer:Carbon

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