NEB Class 11 • Physics • Focused Revision

DC Circuits Study Guide: NEB 11 Physics

Replace formula hunting with a repeatable node–branch–loop method. This plan combines retrieval, diagram translation, worked checks and spaced retesting.

Seven-session circuit plan
Kirchhoff sign and network routines
Meter, graph and power transfer tasks

Node and loop rules turn a drawing into conservation equations.

Revision boundary

Start from the curriculum and a trustworthy concept base

Check the CDC Physics Grade 11 page for the official Nepal context. Use the paired DC Circuits concept guide, the earlier potential-difference study guide and OpenStax resistor networks.

Your aim is evidence, not time spent. End each session with an empty-page explanation, a correctly labelled circuit, checked calculations and one retest date. Reading a worked solution feels fluent but does not prove that you can choose the model independently.

Knowledge map

Organise the chapter around two conservation laws

Charge

I=ΔQ/Δt and junction rule. Charge flow is continuous in steady state.

Energy

Potential rises and drops sum to zero around a loop.

Elements

Resistors, sources and meters each have a model and connection rule.

Checks

Bounds, sums, signs, units and source-power balance expose mistakes.

Put every formula under one of these headings. R=ρL/A is an element model; series and parallel rules follow from shared current or voltage; Kirchhoff rules express conservation; meter rules reduce disturbance of the measured circuit.

Seven sessions

A spaced plan with visible exit evidence

Session	Focus	Required evidence
1	Current, voltage, resistance and I–V graphs	12 retrieval cards and 5 graph interpretations
2	Series, parallel and node marking	8 networks classified before calculation
3	Mixed networks and power	5 full branch-value audits
4	Emf, internal resistance and terminal voltage	6 source/load problems
5	Junction and loop rules	4 simultaneous-equation circuits
6	Meters, graphs and practical evaluation	One plan, data table and uncertainty critique
7	Timed mixed paper and error repair	80% plus no repeated sign/topology error

Space sessions over at least a week. Before each new session, retrieve the previous session’s central rule without notes. Retest failed problems after 48 hours with values or circuit orientation changed.

Diagram-to-equation routine

Use the same eight decisions every time

Copy the circuit cleanly and label every distinct node.
Mark source polarity, resistor value and meter location.
Draw branch-current arrows.
Combine only genuine series or parallel groups.
Write junction equations from charge conservation.
Choose loop directions and create a sign table.
Solve, then recover every branch current and voltage.
Check node current, loop voltage and power balance.

Sign-card drill

Make four cards: resistor with chosen current (+IR against, −IR with); source (− to + gives +ε, + to − gives −ε). Walk around a drawn loop and say each change aloud before writing the equation. Direction is a bookkeeping choice, not a prediction.

When a current solution is negative, keep the magnitude and reverse the arrow in the interpretation. Do not rewrite all equations merely to force a positive number.

Calculation ladder

Move from topology to power without skipping levels

Level 1: two resistors

For 4 Ω and 12 Ω, series R=16 Ω; parallel R=3 Ω. State the bound before calculating.

Level 2: mixed network

Put 4 Ω in series with 12 Ω∥6 Ω. The parallel pair is 4 Ω, so total is 8 Ω. At 16 V, total current is 2 A; both 4 Ω sections drop 8 V. Branch currents are 8/12=0.667 A and 8/6=1.333 A.

Level 3: power audit

Source power is 16×2=32 W. Series 4 Ω uses I²R=16 W. Parallel elements use V²/R: 5.33 W and 10.67 W. Total 32 W, allowing for rounding.

Level 4: real source

If ε=16.5 V and internal r=0.25 Ω feeds the same 8 Ω load, I=16.5/8.25=2.0 A and terminal voltage is 16.0 V. Internal loss is 1.0 W; chemical-source power is εI=33 W.

After each problem, change one connection from series to parallel and predict whether source current rises or falls before calculating.

Loop mastery

Build equations symbolically before numbers

Review the institutional Kirchhoff rules explanation. For a two-loop circuit sharing R₃, choose mesh or branch currents and write the shared-resistor current carefully. If branch current through R₃ is I₁−I₂, the voltage term must use that expression with a sign set by traversal.

Keep equations symbolic through setup: ε₁−I₁R₁−(I₁−I₂)R₃=0 and ε₂−I₂R₂+(I₁−I₂)R₃=0 are easier to audit than prematurely substituted decimals. Solve by elimination, substitute into the junction rule, then evaluate every loop sum numerically.

Reverse-source transfer

After solving a circuit, reverse ε₂ only. Before recalculation, predict which branch current may reverse and whether the shared branch magnitude grows or shrinks. This tests physical interpretation beyond simultaneous-equation mechanics.

Practical and simulation

Collect evidence without letting the meter redefine the circuit

Use the PhET Circuit Construction Kit DC virtual lab to predict series and parallel readings. Then, with teacher-approved low-voltage equipment, measure a resistor’s I–V data. An ammeter goes in series; a voltmeter goes across the resistor. Start at zero, avoid heating, switch off before rewiring and record instrument resolution.

Plot V on the vertical axis and I on the horizontal axis if you want slope R. Repeat readings and look for curvature as temperature changes. A nonzero intercept may represent meter zero error or contact effects. State that real meters have resistance: an ammeter adds a small series resistance and a voltmeter draws a small parallel current.

Never connect school meters or improvised circuits to household mains. Rehearse connection decisions in simulation and follow the laboratory’s current limits and teacher instructions.

Timed transfer test

A forty-minute mixed paper

Define current and distinguish electron drift from conventional current.
Infer resistance and ohmic behaviour from an I–V graph.
Use R=ρL/A to compare two wires.
Reduce a mixed four-resistor network.
Recover every branch current and voltage.
Find terminal voltage and internal loss.
Write junction and loop equations for a two-loop circuit.
Place meters and predict readings.
Compare source power with resistor dissipation.
Evaluate an I–V practical method and safety.

Mark one point each for topology, conservation equation, sign convention, substitution, unit, bound and physical interpretation. A correct number with an impossible parallel equivalent resistance is not secure understanding.

After marking, classify errors as concept, representation, algebra, unit, check or explanation. Repair only the first wrong decision, then solve a contrast problem from an empty page. Use OpenStax circuit exercises for additional institutional practice and the KTM Tuition practice set for the planned sequence.

For online or physical NEB tuition, call 9846662070.

Frequently asked questions

Questions students ask while studying DC circuits

What should I revise before DC circuits?

Revise charge, current, potential difference, energy and basic algebra, then mark nodes before using network formulas.

How do I remember series and parallel rules?

Derive them from same current in series and same voltage in parallel, then use equivalent-resistance bounds.

How many Kirchhoff equations are needed?

Use enough independent junction and loop equations to match the number of unknown branch currents.

Why does a negative current appear?

Your chosen arrow was opposite to the real direction; the magnitude and remaining equations can still be correct.

How should I practise circuit diagrams?

Classify nodes and branches first, predict behaviour, solve symbolically and check charge, voltage and power.

Where can I get revision help?

Call 9846662070 for current online or physical NEB tuition schedules and fees.

References and next steps

Sources and related study guides

Use the concept guide for definitions and the practice set for timed transfer. Curriculum scope and linked institutional sources were checked on 2 August 2026; follow current CDC, NEB, school and laboratory instructions if requirements change.

Oral explanation drill

Prove that the equations match the physical story

Choose one solved mixed network and explain it without reading algebra. Begin at the source: each coulomb receives energy ε, loses part inside the source if internal resistance is present, and transfers the remainder in external elements. At a node, divide current according to branch resistance while the branch endpoints keep a common voltage. When branches reunite, their currents sum to the original current.

Next redraw the same electrical network in a different shape. Node labels must remain unchanged even when components move on the page. Solve again and confirm that readings do not depend on artistic layout. Then swap the positions of an ammeter and a voltmeter in a copy and explain why the circuit model becomes invalid or strongly disturbed.

Finish with a sensitivity question: increase one parallel resistance. Predict the branch current, total equivalent resistance, source current and power before calculating. This prediction–calculation–explanation cycle is a stronger study record than copying another worked solution.

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