JEE Main Previous Year Questions (2025): Electromagnetic Waves

 Page 1


JEE Main Previous Year Questions 
(2025): Electromagnetic Waves 
 
Q1: A parallel plate capacitor of area ?? = ???? ????
?? and separation between the plates 
???? ???? , is charged by a DC current. Consider a hypothetical plane surface of area ?? ?? =
?? . ?? ????
?? inside the capacitor and parallel to the plates. At an instant, the current 
through the circuit is 6 A . At the same instant the displacement current through ?? ?? is 
_ _ _ _ mA. 
JEE Main 2025 (Online) 22nd January Evening Shift 
Ans: 1200 
Solution: 
To determine the displacement current through a hypothetical plane surface within a parallel 
plate capacitor, follow these steps: 
Current Density Calculation: 
The current density ( ?? ?? ) is the current ( ?? ) divided by the area ( ?? ) of the capacitor plates. 
Given: ?? = 6 A and ?? = 16 cm
2
. 
?? ?? =
?? ?? =
6 A
16 cm
2
 
Displacement Current Through the Hypothetical Surface: 
The hypothetical surface has an area ?? 0
= 3 . 2 cm
2
. 
The displacement current through this smaller area ( ?? small 
 ) is the current density multiplied by 
the area of the hypothetical surface. 
?? small 
= ?? ?? × ?? 0
=
6 A
16 cm
2
× 3 . 2 cm
2
 
Calculation: 
Simplify the expression to find the displacement current: 
?? small 
= (
6
16
) × 3 . 2 = 1 . 2 A = 1200 mA 
Thus, the displacement current through the hypothetical plane surface is 1200 mA . 
Q2: A time varying potential difference is applied between the plates of a parallel 
plate capacitor of capacitance ?? . ?? ?? ?? . The dielectric constant of the medium between 
the capacitor plates is 1 . It produces an instantaneous displacement current of 0.25 
mA in the intervening space between the capacitor plates, the magnitude of the rate 
of change of the potential difference will be _ _ _ _ ????
- ?? . 
JEE Main 2025 (Online) 23rd January Evening Shift 
Page 2


JEE Main Previous Year Questions 
(2025): Electromagnetic Waves 
 
Q1: A parallel plate capacitor of area ?? = ???? ????
?? and separation between the plates 
???? ???? , is charged by a DC current. Consider a hypothetical plane surface of area ?? ?? =
?? . ?? ????
?? inside the capacitor and parallel to the plates. At an instant, the current 
through the circuit is 6 A . At the same instant the displacement current through ?? ?? is 
_ _ _ _ mA. 
JEE Main 2025 (Online) 22nd January Evening Shift 
Ans: 1200 
Solution: 
To determine the displacement current through a hypothetical plane surface within a parallel 
plate capacitor, follow these steps: 
Current Density Calculation: 
The current density ( ?? ?? ) is the current ( ?? ) divided by the area ( ?? ) of the capacitor plates. 
Given: ?? = 6 A and ?? = 16 cm
2
. 
?? ?? =
?? ?? =
6 A
16 cm
2
 
Displacement Current Through the Hypothetical Surface: 
The hypothetical surface has an area ?? 0
= 3 . 2 cm
2
. 
The displacement current through this smaller area ( ?? small 
 ) is the current density multiplied by 
the area of the hypothetical surface. 
?? small 
= ?? ?? × ?? 0
=
6 A
16 cm
2
× 3 . 2 cm
2
 
Calculation: 
Simplify the expression to find the displacement current: 
?? small 
= (
6
16
) × 3 . 2 = 1 . 2 A = 1200 mA 
Thus, the displacement current through the hypothetical plane surface is 1200 mA . 
Q2: A time varying potential difference is applied between the plates of a parallel 
plate capacitor of capacitance ?? . ?? ?? ?? . The dielectric constant of the medium between 
the capacitor plates is 1 . It produces an instantaneous displacement current of 0.25 
mA in the intervening space between the capacitor plates, the magnitude of the rate 
of change of the potential difference will be _ _ _ _ ????
- ?? . 
JEE Main 2025 (Online) 23rd January Evening Shift 
Ans: 100 
Solution: 
????
????
=
?? ?? 
Given that the displacement current is ?? = 0 . 25 × 10
- 3
 A and the capacitance is ?? = 2 . 5 ×
10
- 6
 F, the rate of change of the potential difference is calculated as follows: 
????
????
=
0 . 25 × 10
- 3
2 . 5 × 10
- 6
=
0 . 25
2 . 5
×
10
- 3
10
- 6
= 0 . 1 × 10
3
= 100 V / s 
Thus, the magnitude of the rate of change of the potential difference is 100 V / s.