💡 Ohm's Law Circuit Simulator - Current Electricity
Current ElectricityWhat's happening? I = V/R. More voltage = more current = brighter bulb. More resistance = less current = dimmer bulb. Watch the green particles flow faster with higher current.
Current Electricity is one of the highest-weightage topics — often 4-5 questions per paper.
From Ohm's law to Kirchhoff's laws, Wheatstone bridge to meter bridge, this entire unit is concept-driven and highly scoring. JEE tests both numerical problems and circuit analysis.
Key formulas
Current Electricity Formulas
Ohm's Law
V = IR
Voltage = Current × Resistance. Only valid for ohmic materials at constant T.
Resistance
R = ρL/A
ρ = resistivity (Ω·m), L = length, A = cross-sectional area. R ∝ L/A.
Power dissipated
P = VI = I²R = V²/R
Use I²R when current is known, V²/R when voltage is known.
Series & Parallel
Req = R₁ + R₂ + ... (series)
1/Req = 1/R₁ + 1/R₂ + ... (parallel)
Kirchhoff's Laws
ΣI = 0 at any junction
ΣV = 0 in any closed loop
Junction law: current in = current out. Loop law: emfs = IR drops.
Wheatstone Bridge
R₁/R₂ = R₃/R₄
Balanced condition — no current through galvanometer.
Step-by-step problem solving
How to solve current electricity problems in JEE
- Identify the circuit structure — series, parallel, or combination. Label all emfs, resistances, and currents.
- Apply Kirchhoff's laws — junction law (ΣI = 0) and loop law (ΣV = 0) to set up equations.
- Simplify where possible — use series/parallel formulas or convert star-delta for complex networks.
- Solve for unknowns — usually current through a specific branch or voltage across components.
- Check with physical intuition — current flows from high to low potential, voltage drops in direction of current.
Common JEE mistakes
What students get wrong
❌ Wrong current direction
Current flows from higher potential to lower potential through a resistor. In the external circuit of a cell, current flows from positive to negative terminal.
❌ Mixing up V = IR and V = E
V = IR is for resistors. E (emf) is the energy supplied per charge by a source. Terminal voltage V = E - Ir (where r is internal resistance).
❌ Forgetting internal resistance
Real cells have internal resistance r. Terminal voltage V = E - Ir, not just E. This causes voltage to drop under load.
❌ Power formula mix-up
P = VI uses terminal voltage V, not emf E. For a cell: P = EI - I²r.
FAQs
Current Electricity Questions
Why does current split in parallel but voltage splits in series?
In series, current has only one path — same everywhere, so voltage divides. In parallel, each branch gets the full voltage, so current divides inversely with resistance.
Is V = IR always true?
No — only for ohmic materials (constant resistance). Diodes, transistors, and filament bulbs are non-ohmic.
How does a Wheatstone bridge work?
When R₁/R₂ = R₃/R₄, the potential at the two midpoints is equal — no current flows through the galvanometer.
What's the difference between drift velocity and current?
Drift velocity vd = I/(nAe) is the average speed of electrons. Current I = neAvd is the rate of charge flow.