A battery of e. m. f. and internal resistance is connected to an external resistance the condition for maximum power transfer is
1
2
3
4
Official Solution
Correct Option: (4)
We know that the current in the circuit
and power delivered to the resistance is
It is maximum when
or or
02
PYQ 2009
easy
physicsID: wbjee-20
Two identical cells each of emf and internal resistance are connected in parallel with an external resistance . To get maximum power developed across , the value of is
1
R = r/2
2
R = r
3
R = r/3
4
R = 2r
Official Solution
Correct Option: (1)
Equivalent resistance
For maximum power consumption should be maximum so denominator is minimum. For this
03
PYQ 2009
medium
physicsID: wbjee-20
One of copper is drawn into a wire of mm diameter and a wire of mm diameter. The resistance of the two wires will be in the ratio
1
2
3
4
Official Solution
Correct Option: (3)
Mass of 1st wire Mass of Il nd wire
04
PYQ 2009
medium
physicsID: wbjee-20
A wire of resistance is drawn out so that its new length is times its original length.What is the resistance of the new wire?
1
2
3
4
Official Solution
Correct Option: (1)
Since, volume is constant, i.e.,
Now,
05
PYQ 2010
medium
physicsID: wbjee-20
The reading of the ammeter in the following figure will be
1
0.8 A
2
0.6 A
3
0.4 A
4
0.2 A
Official Solution
Correct Option: (3)
Current
06
PYQ 2010
medium
physicsID: wbjee-20
A wire of resistance is elongated -fold to make a new uniform wire. The resistance of new wire
1
2
3
4
Official Solution
Correct Option: (2)
The resistance of a wire is directly proportional to the length of the wire. Thus, so the length increases -fold also since the volume of the wire remains constant, so the area of the wire decreases -fold. Hence the resistance increases to as the area is inversely proportional to resistance.
07
PYQ 2010
medium
physicsID: wbjee-20
The reading of the ammeter in the following figure will be
1
0.8 A
2
0.6 A
3
0.4 A
4
0.2 A
Official Solution
Correct Option: (3)
08
PYQ 2011
easy
physicsID: wbjee-20
Two cells with the same e.m.f. and different internal resistances and are connected in series to an external resistance . The value of so that the potential difference across the first cell be zero is
1
2
3
4
Official Solution
Correct Option: (3)
There are two batteries with emf each and the internal resistances and respectively. Hence we have thus, Now the potential difference across the first cell would be equal to From the question, , hence, , thus, , hence . So, the correct option is (C) : .
09
PYQ 2011
medium
physicsID: wbjee-20
The charge on the capacitor of capacitance shown in the figure below will be
1
2
3
4
Official Solution
Correct Option: (3)
From the figure, we see that the current in the circuit would be equal to
As no current flows through the capacitance in a DC connection. Thus, we get Thus, the potential across the resistance is equal to
and thus the charge on the capacitor would be equal to
10
PYQ 2012
medium
physicsID: wbjee-20
A Wheatstone bridge has the resistances and in its four arms. What resistance joined in parallel to the resistance will bring it to the balanced condition?
1
2
3
4
Official Solution
Correct Option: (4)
In balanced Wheatstone bridge,
11
PYQ 2012
medium
physicsID: wbjee-20
What current will flow through the resistor in the circuit shown in the figure?
1
3 mA
2
6 mA
3
12 mA
4
36 mA
Official Solution
Correct Option: (1)
From KCL we have
12
PYQ 2014
medium
physicsID: wbjee-20
A circuit consists of three batteries of emf and and internal resistances and respectively which are connected in parallel as shown in the figure . The potential difference between points and is
1
1.0 V
2
2.0 V
3
2.2 V
4
3.0 V
Official Solution
Correct Option: (2)
and are in parallel So, the required internal resistance
The potential difference between points and
13
PYQ 2015
medium
physicsID: wbjee-20
A metal wire of circular cross-section has a resistance . The wire is now stretched without breaking so that its length is doubled and the density is assumed to remain the same. If the resistance of the wire now becomes then is
1
1:01
2
1:02
3
4:01
4
1:04
Official Solution
Correct Option: (3)
As we know that, where, length of wire area of cross-section of the wire and volume of the wire
14
PYQ 2018
medium
physicsID: wbjee-20
Four resistors and are connected to form four sides of a square. The resistors can be connected in any order. What is the maximum possible equivalent resistance across the diagonal of the square ?
1
2
3
4
Official Solution
Correct Option: (4)
For maximum equivalent resistance across the diagonal of the square, the given resistors connected as
15
PYQ 2018
medium
physicsID: wbjee-20
What will be current through the resistor in the given circuit a long time after the switch �K� is made on ?
1
Zero
2
100 mA
3
10 mA
4
1 mA
Official Solution
Correct Option: (3)
16
PYQ 2024
hard
physicsID: wbjee-20
Consider a circuit where a cell of emf and internal resistance is connected across the terminal A and B as shown in the figure. The value of for which the power generated in the circuit is maximum, is given by:
1
2
3
4
Official Solution
Correct Option: (3)
Step 1: The total resistance in the circuit is the sum of the internal resistance and the external resistance .
Step 2: The power generated in the circuit is given by:
where is the total resistance in the circuit.
Step 3: To find the value of that maximizes the power, we take the derivative of the power with respect to and set it equal to zero:
Simplifying, we find:
Thus, the value of for which the power is maximum is .
