Current Electricity: JEE Main Previous Year Questions (2021-2026)

 Page 1


JEE Main Previous Year Questions (2021-2026): 
Current Electricity  
 
(January 2026) 
 
Q1: Which one of the following is not a measurable quantity? 
(a) Resistance 
(b) Voltage difference 
(c) Displacement current 
(d) Voltage 
Ans: (d) 
Sol:  
Resistance is a physical property of a conductor that opposes current. It is easily measured 
using an Ohmmeter or by calculating the ratio of voltage to current ( R = V/I).  
Hence, option (A) is not the correct option. The voltage of a single point is representing the 
electric potential of that point which is defined as the work done to move a unit charge from 
infinity to a specific point.  
Since infinity is an arbitrary reference point, the absolute value of voltage at a single point 
cannot be measured directly. It is a mathematical construct. So, voltage cannot be measured, 
i.e., not a measurebale quantity. Hence, option is (D) is the correct option.  
Voltage difference (Potential difference) is the difference in electric potential between two 
specific points. This is measured by a voltmeter. So, it is a measurable quantity. Hence, option 
(B) is not the correct option.  
Displacement current is a quantity appearing in Maxwell's equations, representing a changing 
electric field (like between the plates of a capacitor). While it isn't a flow of charges like normal 
current, its magnetic effects are real and can be measured using magnetic sensors. Hence, it is 
a measurable quantity. So option (C) is not the correct option.  
Therefore, the correct option is (D). 
 
Q2: A Wheatstone bridge is initially at room temperature and all arms of the bridge have 
same value of resistances (R
1
 = R
2
 = R
3
 = R
4
). When R
3
 resistance is heated to some 
temperature, its resistance value has gone up by 10%. The potential difference (V
a
 - V
b
) 
(after R
3
 is heated) is _________ V. 
Page 2


JEE Main Previous Year Questions (2021-2026): 
Current Electricity  
 
(January 2026) 
 
Q1: Which one of the following is not a measurable quantity? 
(a) Resistance 
(b) Voltage difference 
(c) Displacement current 
(d) Voltage 
Ans: (d) 
Sol:  
Resistance is a physical property of a conductor that opposes current. It is easily measured 
using an Ohmmeter or by calculating the ratio of voltage to current ( R = V/I).  
Hence, option (A) is not the correct option. The voltage of a single point is representing the 
electric potential of that point which is defined as the work done to move a unit charge from 
infinity to a specific point.  
Since infinity is an arbitrary reference point, the absolute value of voltage at a single point 
cannot be measured directly. It is a mathematical construct. So, voltage cannot be measured, 
i.e., not a measurebale quantity. Hence, option is (D) is the correct option.  
Voltage difference (Potential difference) is the difference in electric potential between two 
specific points. This is measured by a voltmeter. So, it is a measurable quantity. Hence, option 
(B) is not the correct option.  
Displacement current is a quantity appearing in Maxwell's equations, representing a changing 
electric field (like between the plates of a capacitor). While it isn't a flow of charges like normal 
current, its magnetic effects are real and can be measured using magnetic sensors. Hence, it is 
a measurable quantity. So option (C) is not the correct option.  
Therefore, the correct option is (D). 
 
Q2: A Wheatstone bridge is initially at room temperature and all arms of the bridge have 
same value of resistances (R
1
 = R
2
 = R
3
 = R
4
). When R
3
 resistance is heated to some 
temperature, its resistance value has gone up by 10%. The potential difference (V
a
 - V
b
) 
(after R
3
 is heated) is _________ V. 
 
(a) 1.05 
(b) 0.95 
(c) 0 
(d) 2 
Ans: (b) 
Sol: 
Initially: R
1
 = R
2
 = R
3
 = R
4
 = R.  
After heating R
3
 :  
1. R
1
 = R  
2. R
2
 = R  
3. R
3
 = R + 10 % of R = 1.1 R  
4. R
4
 = R  
Supply voltage V = 40 V. 
Page 3


JEE Main Previous Year Questions (2021-2026): 
Current Electricity  
 
(January 2026) 
 
Q1: Which one of the following is not a measurable quantity? 
(a) Resistance 
(b) Voltage difference 
(c) Displacement current 
(d) Voltage 
Ans: (d) 
Sol:  
Resistance is a physical property of a conductor that opposes current. It is easily measured 
using an Ohmmeter or by calculating the ratio of voltage to current ( R = V/I).  
Hence, option (A) is not the correct option. The voltage of a single point is representing the 
electric potential of that point which is defined as the work done to move a unit charge from 
infinity to a specific point.  
Since infinity is an arbitrary reference point, the absolute value of voltage at a single point 
cannot be measured directly. It is a mathematical construct. So, voltage cannot be measured, 
i.e., not a measurebale quantity. Hence, option is (D) is the correct option.  
Voltage difference (Potential difference) is the difference in electric potential between two 
specific points. This is measured by a voltmeter. So, it is a measurable quantity. Hence, option 
(B) is not the correct option.  
Displacement current is a quantity appearing in Maxwell's equations, representing a changing 
electric field (like between the plates of a capacitor). While it isn't a flow of charges like normal 
current, its magnetic effects are real and can be measured using magnetic sensors. Hence, it is 
a measurable quantity. So option (C) is not the correct option.  
Therefore, the correct option is (D). 
 
Q2: A Wheatstone bridge is initially at room temperature and all arms of the bridge have 
same value of resistances (R
1
 = R
2
 = R
3
 = R
4
). When R
3
 resistance is heated to some 
temperature, its resistance value has gone up by 10%. The potential difference (V
a
 - V
b
) 
(after R
3
 is heated) is _________ V. 
 
(a) 1.05 
(b) 0.95 
(c) 0 
(d) 2 
Ans: (b) 
Sol: 
Initially: R
1
 = R
2
 = R
3
 = R
4
 = R.  
After heating R
3
 :  
1. R
1
 = R  
2. R
2
 = R  
3. R
3
 = R + 10 % of R = 1.1 R  
4. R
4
 = R  
Supply voltage V = 40 V. 
 
The voltage across R
1
 and R
2
 is 40 V. So the current in this branch is  
The voltage across 
 
The voltage across 
 
Assuming the potential of negative terminal of battery as 0V then v
a
 = V
2
 = 20 V  
Similarly for the branch containing R
3
 and R
4
,  
The voltage across R
3
 and R
4
 is 40 V.  
So the current in this branch is  
 
Assuming the potential of negative terminal of battery as 0 V then v
b
 = V
4
 = 19.05 V  
So, the potential difference between points a and b is,  
(V
a
 - V
b
) = 20 V - 19.05 V = 0.95 V  
Page 4


JEE Main Previous Year Questions (2021-2026): 
Current Electricity  
 
(January 2026) 
 
Q1: Which one of the following is not a measurable quantity? 
(a) Resistance 
(b) Voltage difference 
(c) Displacement current 
(d) Voltage 
Ans: (d) 
Sol:  
Resistance is a physical property of a conductor that opposes current. It is easily measured 
using an Ohmmeter or by calculating the ratio of voltage to current ( R = V/I).  
Hence, option (A) is not the correct option. The voltage of a single point is representing the 
electric potential of that point which is defined as the work done to move a unit charge from 
infinity to a specific point.  
Since infinity is an arbitrary reference point, the absolute value of voltage at a single point 
cannot be measured directly. It is a mathematical construct. So, voltage cannot be measured, 
i.e., not a measurebale quantity. Hence, option is (D) is the correct option.  
Voltage difference (Potential difference) is the difference in electric potential between two 
specific points. This is measured by a voltmeter. So, it is a measurable quantity. Hence, option 
(B) is not the correct option.  
Displacement current is a quantity appearing in Maxwell's equations, representing a changing 
electric field (like between the plates of a capacitor). While it isn't a flow of charges like normal 
current, its magnetic effects are real and can be measured using magnetic sensors. Hence, it is 
a measurable quantity. So option (C) is not the correct option.  
Therefore, the correct option is (D). 
 
Q2: A Wheatstone bridge is initially at room temperature and all arms of the bridge have 
same value of resistances (R
1
 = R
2
 = R
3
 = R
4
). When R
3
 resistance is heated to some 
temperature, its resistance value has gone up by 10%. The potential difference (V
a
 - V
b
) 
(after R
3
 is heated) is _________ V. 
 
(a) 1.05 
(b) 0.95 
(c) 0 
(d) 2 
Ans: (b) 
Sol: 
Initially: R
1
 = R
2
 = R
3
 = R
4
 = R.  
After heating R
3
 :  
1. R
1
 = R  
2. R
2
 = R  
3. R
3
 = R + 10 % of R = 1.1 R  
4. R
4
 = R  
Supply voltage V = 40 V. 
 
The voltage across R
1
 and R
2
 is 40 V. So the current in this branch is  
The voltage across 
 
The voltage across 
 
Assuming the potential of negative terminal of battery as 0V then v
a
 = V
2
 = 20 V  
Similarly for the branch containing R
3
 and R
4
,  
The voltage across R
3
 and R
4
 is 40 V.  
So the current in this branch is  
 
Assuming the potential of negative terminal of battery as 0 V then v
b
 = V
4
 = 19.05 V  
So, the potential difference between points a and b is,  
(V
a
 - V
b
) = 20 V - 19.05 V = 0.95 V  
Therefore, the potential difference is 0.95 V. Hence, the correct option is (b). 
 
Q3: For the two cells having same EMF E and internal resistance r , the current passing 
through the external resistor 6 O is same when both the cells are connected either in 
parallel or in series. The value of internal resistance r is ____O.  
(a) 3  
(b) 6  
(c) 4  
(d) 9  
Ans: (b) 
Sol: 
Case 1: when cells are in series :  
When two identical cells (E, r) are connected in series with an external resistor R = 6O: 
 
Total EMF E
eq
 = E + E = 2 E  
Total internal resistance r
eq
 = r + r = 2 r  
So, the current in the circuit is, 
 
Case 2: Cells in Parallel When two identical cells (E, r) are connected in parallel with an 
external resistor R = 6 O: 
 
Equivalent EMF (E
eq
) in parallel is given as  
Page 5


JEE Main Previous Year Questions (2021-2026): 
Current Electricity  
 
(January 2026) 
 
Q1: Which one of the following is not a measurable quantity? 
(a) Resistance 
(b) Voltage difference 
(c) Displacement current 
(d) Voltage 
Ans: (d) 
Sol:  
Resistance is a physical property of a conductor that opposes current. It is easily measured 
using an Ohmmeter or by calculating the ratio of voltage to current ( R = V/I).  
Hence, option (A) is not the correct option. The voltage of a single point is representing the 
electric potential of that point which is defined as the work done to move a unit charge from 
infinity to a specific point.  
Since infinity is an arbitrary reference point, the absolute value of voltage at a single point 
cannot be measured directly. It is a mathematical construct. So, voltage cannot be measured, 
i.e., not a measurebale quantity. Hence, option is (D) is the correct option.  
Voltage difference (Potential difference) is the difference in electric potential between two 
specific points. This is measured by a voltmeter. So, it is a measurable quantity. Hence, option 
(B) is not the correct option.  
Displacement current is a quantity appearing in Maxwell's equations, representing a changing 
electric field (like between the plates of a capacitor). While it isn't a flow of charges like normal 
current, its magnetic effects are real and can be measured using magnetic sensors. Hence, it is 
a measurable quantity. So option (C) is not the correct option.  
Therefore, the correct option is (D). 
 
Q2: A Wheatstone bridge is initially at room temperature and all arms of the bridge have 
same value of resistances (R
1
 = R
2
 = R
3
 = R
4
). When R
3
 resistance is heated to some 
temperature, its resistance value has gone up by 10%. The potential difference (V
a
 - V
b
) 
(after R
3
 is heated) is _________ V. 
 
(a) 1.05 
(b) 0.95 
(c) 0 
(d) 2 
Ans: (b) 
Sol: 
Initially: R
1
 = R
2
 = R
3
 = R
4
 = R.  
After heating R
3
 :  
1. R
1
 = R  
2. R
2
 = R  
3. R
3
 = R + 10 % of R = 1.1 R  
4. R
4
 = R  
Supply voltage V = 40 V. 
 
The voltage across R
1
 and R
2
 is 40 V. So the current in this branch is  
The voltage across 
 
The voltage across 
 
Assuming the potential of negative terminal of battery as 0V then v
a
 = V
2
 = 20 V  
Similarly for the branch containing R
3
 and R
4
,  
The voltage across R
3
 and R
4
 is 40 V.  
So the current in this branch is  
 
Assuming the potential of negative terminal of battery as 0 V then v
b
 = V
4
 = 19.05 V  
So, the potential difference between points a and b is,  
(V
a
 - V
b
) = 20 V - 19.05 V = 0.95 V  
Therefore, the potential difference is 0.95 V. Hence, the correct option is (b). 
 
Q3: For the two cells having same EMF E and internal resistance r , the current passing 
through the external resistor 6 O is same when both the cells are connected either in 
parallel or in series. The value of internal resistance r is ____O.  
(a) 3  
(b) 6  
(c) 4  
(d) 9  
Ans: (b) 
Sol: 
Case 1: when cells are in series :  
When two identical cells (E, r) are connected in series with an external resistor R = 6O: 
 
Total EMF E
eq
 = E + E = 2 E  
Total internal resistance r
eq
 = r + r = 2 r  
So, the current in the circuit is, 
 
Case 2: Cells in Parallel When two identical cells (E, r) are connected in parallel with an 
external resistor R = 6 O: 
 
Equivalent EMF (E
eq
) in parallel is given as  
 
As the internal resistances are in parallel, equivalent internal resistance (r
eq
): 
 
Hence, the current through external resistor is 
 
According to the question, i
s
 = i
p
: 
 
So, the value of internal resistance r is 6 O.  
Hence, the correct option is (b). 
 
 
Q4: In the potentiometer, when the cell in the secondary circuit is shunted with 4O 
resistance, the balance is obtained at the length 120 cm of wire. Now when the same cell 
is shunted with 12 O resistance, the balance is shifted to a length of 180 cm . The internal 
resistance of cell is ______O  
(a) 4  
(b)12  
(c) 6  
(d) 3  
Ans: (a) 
Sol: 
Let the current in the primary circuit is i
p
. If the resistance of potentiometer wire of length L is R, 
then the resistance of the balancing length