What the board asks
We went through the ISC board papers, question by question, and matched each question to a topic. Here is what was asked, how often, and what was never asked.
Physics: 427 topics in the 2027 syllabus, across 9 units. The board has asked 269 of them at least once. 158 were never asked in the papers we checked.
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P2 Current Electricity
All the topics in Physics: Current Electricity
Asked topics first, the most asked at the top. Tap a topic to see what to write, the result, the years, and the real board questions.
45 topics shown
| # | Topic | Type | Marks | Times asked | Last asked | Status |
|---|---|---|---|---|---|---|
| 1 | Numericals: two-loop network with two batteries (Kirchhoff)Label the branch currents (I1, I2 and I1 + I2), write the loop equation for two independent loops including the internal resistances, solve the two simultaneous equations, and read a negative answer as a current opposite to the assumed direction. | Numericals | 3 | 5 papers | 2025 improvement | Asked |
| 2 | Numericals: series-parallel resistor network, ammeter readingReduce a network of resistors to one equivalent resistance step by step (spotting which are in parallel even when drawn diagonally), add the battery's internal resistance, and find the main current or ammeter reading and, if asked, a branch current or p.d. | Numericals | 3 | 4 papers | Specimen 2027 | Asked |
| 3 | Numericals: identical cells in series, parallel, mixed groupingFind the emf and internal resistance of a battery built from identical cells in series, in parallel or as rows in parallel, then the current through an external resistor, and compare the currents given by two groupings. | Numericals | 3 | 4 papers | Specimen 2027 | Asked |
| 4 | Give reasons: how drift speed and relaxation time changeFor a metallic wire, state with a one-line reason from vd = e V tau/(m l) = I/(n A e) how drift speed, relaxation time and mobility respond when V, I, length, area or temperature is changed, including when the information is given as a J against E graph. | Give reason | 2 | 4 papers | 2026 | Asked |
| 5 | Numericals: power, rated appliances, bulbs in series or parallelFrom a rating (V, P) find the working current and the filament resistance, then the current or power when such appliances are joined in series or in parallel across a supply, and the power shared between resistors in a given combination. | Numericals | 2 | 4 papers | 2026 | Asked |
| 6 | Give reasons: power against R, bulb brightness, P-I graphExplain when P is proportional to R (same current, series) and when to 1/R (same potential difference, parallel), use this to decide which of several rated bulbs glows brightest in series and in parallel, and identify the shape of the graph of P against I for a wire. | Give reason | 2 | 3 papers | Specimen 2027 | Asked |
| 7 | Numericals: equivalent emf of unequal cells, series and parallelFor a battery of unequal cells, first combine the cells in series in each branch (watching polarity), then combine the branches in parallel, to get the net emf and internal resistance between the terminals. | Numericals | 3 | 3 papers | 2026 | Asked |
| 8 | Numericals: balanced Wheatstone bridge, unknown arm, total currentUse the balance condition to find an unknown arm or the resistance that must be joined (in series or in parallel) to balance the bridge, and for a balanced bridge leave out the galvanometer arm to find the equivalent resistance and the battery current. | Numericals | 3 | 3 papers | 2026 | Asked |
| 9 | Numericals: compare emfs or resistances from balancing lengthsWith the driver circuit unchanged, use direct proportion between the balanced p.d. and the balancing length to find a second emf, a second balancing length, or an unknown resistance from the lengths that balance the p.d.s across a known and an unknown resistor carrying the same current. | Numericals | 2 | 3 papers | 2025 | Asked |
| 10 | Numericals: wire current, potential gradient, balancing lengthFrom the driver emf, its internal resistance, the series resistance and the resistance and length of the wire, find the current in the wire, the p.d. across it and the potential gradient, then the balancing length for a given cell or the emf for a given balancing length. | Numericals | 3 | 3 papers | 2025 improvement | Asked |
| 11 | Potentiometer circuit to compare emfs of two cellsDraw the labelled circuit: driver cell, key and rheostat in series with the wire AB; cells X and Y with their positive terminals joined to A (the end connected to the driver's positive), each through a two-way key to a galvanometer and jockey; then, if asked, give the method in three lines and the formula. | Diagram | 2 | 2 papers | Specimen 2027 | Asked |
| 12 | Numericals: junction rule and one loop, single unknownUse the junction law to find an unknown branch current from the currents marked on a diagram, and the loop law round one closed loop with known currents to find an unknown emf or resistance. | Numericals | 2 | 2 papers | 2026 | Asked |
| 13 | Graphs: resistivity against temperature, metal and semiconductorSketch resistivity (or resistance) against temperature for a metallic conductor (rising) and for a semiconductor (falling steeply), label the axes, and state in words how each varies. | Graph | 2 | 2 papers | 2025 improvement | Asked |
| 14 | Explain temperature effect using rho = m/(n e^2 tau)Use rho = m/(n e^2 tau) to explain why heating a metal raises its resistance (n fixed, collisions more frequent so tau falls) while heating a semiconductor lowers it (n rises sharply and outweighs the fall in tau). | Give reason | 2 | 2 papers | 2025 improvement | Asked |
| 15 | Definitions and units: current, current density, drift velocity, mobilityDefine electric current (I = Q/t), current density (J = I/A, a vector along E), drift velocity, relaxation time, electron mobility and free-electron number density n, each with its SI unit and, where asked, its dimensions. | Statement | 2 | 2 papers | 2023 | Asked |
| 16 | Obtain the relation I = n e A vdTake a conductor of length l and cross-section A with n free electrons per unit volume, find the charge that crosses a section in the time l/vd, and obtain I = n e A vd and hence J = n e vd. | Derivation | 2 | 2 papers | 2023 | Asked |
| 17 | Wheatstone bridge: circuit and balance conditionDraw the four-arm bridge with galvanometer and cell, take Ig = 0 at balance so that the same current flows in each pair of adjacent arms and the two ends of the galvanometer are at one potential, equate the p.d.s across corresponding arms, and divide to get the balance condition. | Derivation | 3 | 2 papers | 2023 | Asked |
| 18 | Give reasons: what resistance and resistivity depend onExplain in two or three lines that R of a given conductor at constant temperature is fixed by rho, l and A and does not change when V or I is varied (V/I stays the same), and that rho depends only on the material and its temperature, not on the dimensions. | Give reason | 2 | 1 paper | Specimen 2027 | Asked |
| 19 | Numericals: metre bridge balance point and unknown resistanceFrom the balance length find the unknown resistance (first combining any resistors joined in series or parallel in a gap), or predict the new balance point when a gap resistance is changed or the two gaps are interchanged. | Numericals | 3 | 1 paper | Specimen 2027 | Asked |
| 20 | State and explain Kirchhoff's two laws, sign conventionState the junction law and the loop law, name the conservation principle behind each (charge, energy), and write the sign rules for the change in potential across a resistor and across a cell, illustrated on one simple loop. | Statement | 2 | 1 paper | 2026 | Asked |
| 21 | Verify Ohm's law experimentally: circuit, readings, graphDraw the labelled circuit (cell, key, rheostat, ammeter in series with the resistor, voltmeter across it), say how V and I are varied and recorded, and sketch the straight-line V-I graph through the origin whose slope gives R. | Diagram | 3 | 1 paper | 2025 | Asked |
| 22 | V-I graphs: ohmic and non-ohmic conductors, meaning of slopeSketch the V-I characteristic of an ohmic conductor (straight line through the origin) and of a non-ohmic one (curved), define each class with examples, and compare two conductors by the slope of their V-I or J-E lines. | Graph | 2 | 1 paper | 2025 | Asked |
| 23 | Cell's V-I graph: read emf and internal resistanceFor a cell joined to a variable resistor with an ammeter in series and a voltmeter across the resistor, explain why terminal p.d. against current is a falling straight line, then read the emf from the intercept on the V axis and the internal resistance from the slope. | Graph | 3 | 1 paper | 2025 | Asked |
| 24 | Give reasons: Wheatstone and metre bridge behaviourAnswer one-line reasoning questions: why the balance point does not move when the battery and the galvanometer are interchanged, what happens to the balance point when the gap resistances are swapped or one of them is increased, and why the galvanometer shows no deflection at balance. | Give reason | 1 | 1 paper | 2024 | Asked |
| 25 | Obtain Ohm's law in vector form J = sigma EStarting from V = IR with R = rho l/A, E = V/l and J = I/A (or from J = n e vd with vd = e E tau/m), show E = rho J and write J = sigma E as a vector relation, saying what each symbol stands for. | Derivation | 2 | 1 paper | 2023 | Asked |
| 26 | Numericals: drift speed, mobility and relaxation timeCompute the drift speed from current, cross-section and number density (converting mm^2 to m^2), and in related problems find the mobility from vd and E, or the relaxation time from resistivity and n. | Numericals | 2 | 1 paper | 2020 | Asked |
| 27 | Numericals: R = rho l/A, stretched and reshaped wiresFind resistance, resistivity or conductivity from the dimensions of a wire, and the new resistance when a wire is stretched (volume constant), cut into parts, or bent into a circle and measured across a diameter. | Numericals | 2 | 1 paper | 2020 | Asked |
| 28 | Potentiometer circuit to measure internal resistance of a cellDraw the labelled circuit with the cell under test joined to the wire through a galvanometer and jockey, and a resistance box R with key K2 across the cell; give the balancing length l1 with K2 open (emf) and l2 with K2 closed (terminal p.d.), and write or derive the working formula. | Diagram | 3 | 1 paper | 2019 | Asked |
| 29 | Derive drift velocity vd = e E tau/mDescribe the random thermal motion of free electrons in a metal (average velocity zero), apply a field E to get the acceleration a = eE/m opposite to E, average over collisions using the relaxation time tau, and arrive at the drift velocity with its direction. | Derivation | 2 | never | Never asked | |
| 30 | Prove Ohm's law; derive rho = m/(n e^2 tau)Combine I = n e A vd with vd = e V tau/(m l) to show that V/I is constant for a given conductor at a fixed temperature (Ohm's law), identify R = m l/(n e^2 tau A), and read off the resistivity and the conductivity. | Derivation | 3 | never | Never asked | |
| 31 | State Ohm's law; define resistance, resistivity, conductance, conductivityState Ohm's law with its condition (physical conditions such as temperature unchanged), define resistance R = V/I, resistivity through R = rho l/A, conductance G = 1/R and conductivity sigma = 1/rho, with the SI unit and dimensions of each. | Statement | 2 | never | Never asked | |
| 32 | Electrical energy and power: formulas, units, kilowatt-hourStarting from the work done W = qV with q = It, write the energy consumed in time t and the power in all three forms, say when each form is the convenient one, and define the watt, the joule and the commercial unit (kilowatt-hour) with its value in joules. | Statement | 2 | never | Never asked | |
| 33 | Numericals: electricity consumption in kWh and the billFor a list of appliances with their wattages and hours of daily use, compute the energy in kilowatt-hours (units) over the stated number of days and the cost at a given rate per unit. | Numericals | 2 | never | Never asked | |
| 34 | Define emf, terminal p.d., internal resistance, back emfDefine the emf of a source as the work done per unit charge in taking charge from the negative to the positive terminal inside it, name the kinds of energy a seat of emf may draw on, and define terminal potential difference, internal resistance and the back emf Ir, with units. | Statement | 2 | never | Never asked | |
| 35 | Derive I = emf/(R+r) and V = emf - IrFrom emf = dW/dq and dq = I dt, equate the work done by the cell in time dt to the energy dissipated in the external resistance R and in the internal resistance r, and obtain the current and the terminal potential difference. | Derivation | 2 | never | Never asked | |
| 36 | Numericals: cell with internal resistance in a circuitFor a cell of given emf and internal resistance joined to an external resistance, find the current, the terminal p.d. and the back emf Ir, or find the internal resistance from the open-circuit and closed-circuit voltmeter readings. | Numericals | 2 | never | Never asked | |
| 37 | Derive current for identical cells in series and parallelFor n identical cells (emf E, internal resistance r) in series, and for m such cells in parallel, across an external R: draw each circuit, write the total emf and total internal resistance, derive the current, and say when each grouping is useful. | Derivation | 3 | never | Never asked | |
| 38 | Derive current for mixed grouping of identical cellsFor m rows in parallel, each row of n identical cells in series, across an external R: draw the arrangement, write the battery emf n E and internal resistance n r/m, and derive the current through R. | Derivation | 3 | never | Never asked | |
| 39 | Equivalent emf of two unequal cells in parallelFor two cells (E1, r1) and (E2, r2) joined in parallel with like terminals together, write I = I1 + I2 with V = E1 - I1 r1 = E2 - I2 r2, eliminate the branch currents, and compare with V = E_eq - I r_eq to get the equivalent emf and internal resistance. | Derivation | 3 | never | Never asked | |
| 40 | Equivalent emf of n unequal cells in seriesFor cells (E1, r1), (E2, r2), ... joined in series, add the terminal p.d.s V = (E1 - I r1) + (E2 - I r2) + ... and compare with V = E_eq - I r_eq; state what changes when one cell is connected in opposition. | Derivation | 2 | never | Never asked | |
| 41 | Metre bridge: labelled diagram, principle, finding unknown resistanceDraw the labelled metre bridge (1 m uniform wire, copper strips with two gaps, known R and unknown X, galvanometer with jockey, cell and key), state that it works as a balanced Wheatstone bridge, show that the two parts of the wire act as the ratio arms (resistance proportional to length), and derive the working formula with the steps of the measurement. | Device | 3 | never | Never asked | |
| 42 | Potentiometer principle, potential gradient, sensitivityState that for a uniform wire carrying a steady current the fall of potential is proportional to the length, define the potential gradient K with its unit, explain how an emf is balanced against the fall of potential over a length l (null point), and say what sensitivity means and how it is increased. | Statement | 2 | never | Never asked | |
| 43 | Potentiometer as a voltmeter; give-reason questionsExplain how a potential difference is measured as V = K l, why a potentiometer gives the true emf of a cell while a voltmeter reads less (no current is drawn from the cell at the null point), and reason out when no balance point is found and how a change in the driver circuit shifts the balance point. | Give reason | 2 | never | Never asked | |
| 44 | Numericals: internal resistance from potentiometer balancing lengthsGiven the balancing lengths with the cell on open circuit and with a known resistance across it, compute the internal resistance of the cell. | Numericals | 2 | never | Never asked | |
| 45 | Numericals: resistance at another temperature (temperature coefficient)Use the linear relation between resistance (or resistivity) and temperature to find the resistance at another temperature, the temperature coefficient alpha, or the temperature at which R reaches a given value. | Numericals | 2 | never | Not in syllabus |
This list was made from the 2027 syllabus and checked with 9 board papers, including the 2027 specimen paper. It is not yet checked with the textbook.
The 10 topics Physics papers ask most
Counted on the board papers from 2018 to the 2027 specimen paper, which every unit has been checked against.
- 1.Numericals: peak, rms, mean, frequency from an ac equationP4 Electromagnetic Induction and Alternating Currents · asked 7 times since 2018
- 2.Uses and special properties of each region (table)P5 Electromagnetic Waves · asked 7 times since 2018
- 3.State Bohr's postulates for the hydrogen atomP8 Atoms and Nuclei · asked 7 times since 2018
- 4.Magnetic force on a moving charge and Lorentz forceP3 Magnetic Effects of Current and Magnetism · asked 6 times since 2018
- 5.Numericals: average power and power factorP4 Electromagnetic Induction and Alternating Currents · asked 6 times since 2018
- 6.Doping, n-type and p-type, donors, acceptors, carriersP9 Electronic Devices · asked 6 times since 2018
- 7.Numericals: two-loop network with two batteries (Kirchhoff)P2 Current Electricity · asked 5 times since 2018
- 8.Derive B at the centre of a circular loopP3 Magnetic Effects of Current and Magnetism · asked 5 times since 2018
- 9.Numericals: B at the centre of a circular coilP3 Magnetic Effects of Current and Magnetism · asked 5 times since 2018
- 10.Ampere's law: derive B near a long straight wireP3 Magnetic Effects of Current and Magnetism · asked 5 times since 2018