Playbook
Current Electricity
82 q - 1.96/paper - 24% HARD. Meter conversions and Kirchhoff are the cheap entry; the bridges are 35% HARD.
- Questions in the bank
- 82
- q/paper (2024–25 papers)
- 1.96
- Tagged HARD
- 24%
- Subtopics
- 5
Strand: Long Tail
When you’ll see it
A network of resistors and cells, a potentiometer or meter bridge, or turning a galvanometer into an ammeter or voltmeter.
How this chapter is tested
82 q at 1.96 a paper, 24% HARD. Galvanometer, Ammeter, and Voltmeter Conversion (24 q, 17%) and Kirchhoff's Laws (19 q, 16%) are the cheap entry. An ammeter is a galvanometer with a small SHUNT in parallel; a voltmeter is one with a large resistance in series.
The bridges carry the HARD: Wheatstone Bridge and Meter Bridge is 17 questions at 35%, and Potentiometer 18 at 28%. A bridge is balanced only when P/Q = R/S; when it is, the galvanometer arm carries no current and can be removed. When it is not — and some that look balanced are not — current flows through that arm and the circuit must be solved with Kirchhoff.
A potentiometer compares EMFs by balancing lengths: E₁/E₂ = l₁/l₂, and the internal resistance r = R(l₁ − l₂)/l₂.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Meter conversion
Shunt S = I_g G/(I − I_g) in parallel for an ammeter; series R = V/I_g − G for a voltmeter.
Kirchhoff's laws
Current in = current out at a junction; the EMFs round a loop equal the IR drops.
Bridges
Balanced when P/Q = R/S. Meter bridge: R/S = l/(100 − l).
Potentiometer
E₁/E₂ = l₁/l₂; r = R(l₁ − l₂)/l₂. Sensitivity rises with the wire's length.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Deleting the galvanometer from an unbalanced bridge
The arm carries no current only when P/Q = R/S. Check the ratio first; a bridge with arms 4, 4, 1 and 3 Ω is not balanced.
Shunt in series
An ammeter's shunt goes in PARALLEL and is small; a voltmeter's resistance goes in SERIES and is large. The two are swapped in the options.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Current Electricity notesDrill every current electricity question
82 questions from the bank, scoped to 5 bundled subtopics.
Drill one subtopic at a time
The 5 subtopics this playbook covers, in catalog order.
Related playbooks
Often paired with this one — the technique, the trap or the taxonomy overlaps. Drill these next.