IIT JEE Physics Electrostatics and Current Electricity practice test with 30 MCQs, solutions, and instant score.
30 Questions | 4 Marks Each | No Negative Marking
Electrostatics & Current Electricity – IIT JEE Notes (Set 2)
Electric Charge and Coulomb’s Law
Basic Concept
Electric charge is a fundamental property of matter. Charges can be positive or negative and interact through electrostatic forces. Like charges repel and unlike charges attract.
Coulomb’s Law
F = k × (q₁q₂ / r²)
The electrostatic force is directly proportional to the product of charges and inversely proportional to the square of the distance between them. This inverse square law is very important for IIT JEE.
Electric Field
Definition
E = F / q
Electric field is the force experienced by a unit positive charge placed in the field.
Important Points
The unit of electric field is N/C. The direction of electric field is the direction of force on a positive charge. Inside a conductor, the electric field is zero due to redistribution of charges.
Electric Potential and Potential Difference
Electric Potential
V = W / q
Electric potential is the work done per unit charge in bringing a charge from infinity to a point.
Potential Difference
It is the difference in potential between two points and is responsible for the flow of current in a circuit.
Capacitance
Definition
C = Q / V
Capacitance is the ability of a conductor to store charge.
Parallel Plate Capacitor
C = ε₀A / d
Capacitance increases with plate area and decreases with distance between plates.
Electric Current
Definition
I = Q / t
Electric current is the rate of flow of charge through a conductor.
Key Concept
Current is caused by drift of electrons under an electric field. Though electrons move randomly, an applied field creates a net motion.
Ohm’s Law
Formula
V = IR
It states that current is directly proportional to voltage for a conductor at constant temperature.
Graph Insight
The V-I graph for an ohmic conductor is a straight line, and its slope represents resistance.
Resistance and Resistivity
Formula
R = ρL / A
Resistance depends on length, area, and material of the conductor.
Important Points
Resistance increases with length and decreases with cross-sectional area. Resistivity is a material property and is independent of shape.
Combination of Resistors
Series Combination
R = R₁ + R₂ + R₃
Same current flows through all resistors, and total resistance increases.
Parallel Combination
1/R = 1/R₁ + 1/R₂ + 1/R₃
Voltage remains the same across resistors, and total resistance decreases.
Electrical Power
Formula
P = VI = I²R = V²/R
Electrical power is the rate at which electrical energy is consumed or converted.
Important Insight
Higher current or voltage increases power. These formulas are frequently used in numerical problems.
Key Exam Concepts
Conceptual Traps
Electric field inside conductor is zero. Work done depends on angle between force and displacement. Resistance does not depend on current or voltage directly.
JEE Strategy
Focus on formulas, units, and conceptual clarity. Practice derivations and numerical problems regularly to strengthen understanding.