The equivalent resistance of two resistors R1 and R2 connected in parallel is:

(a) \frac{\mathrm{R}_1+\mathrm{R}_2}{\mathrm{R}_1\mathrm{R}_2}

(b) \frac{\mathrm{R}_1\mathrm{R}_2}{\mathrm{R}_1+\mathrm{R}_2}

(c) \frac{\mathrm{R}_1-\mathrm{R}_2}{\mathrm{R}_1\mathrm{R}_2}

(d) \frac{\mathrm{R}_1\mathrm{R}_2}{\mathrm{R}_1-\mathrm{R}_2}

Study the circuit diagram containing lamps L1, L2, L3 and L4. Which lamp can fail without interrupting the glow of the other lamps? (a) L1 (b) L2 (c) L3 (d) L4

Bulb A rated 160 W, 40 V and Bulb B rated 40 W, 40 V are connected as shown in the diagram. (a) Calculate the ratio V1 : V2. (b) If bulb A fuses, the current in the circuit remains the same. State True or False.

Complete the following by choosing the correct answers from the bracket: (a) A car is moving in uniform circular motion. The direction of friction between the tyres and the path is ............... [towards the centre / tangential to the path]. (b) When a ray of light passes from a denser to a rarer medium, its wavelength ............... [decreases / increases]. (c) The lid of a calorimeter minimises heat loss by ............... [convection / radiation]. (d) Quality of sound depends on its ............... [amplitude / waveform]. (e) A substance whose resistance becomes almost negligible at a temperature near absolute zero is called a ............... [semiconductor / superconductor]. (f) ............... radiation deviates minimum in a magnetic field [Alpha / Beta].

In the combinations of resistors shown below, calculate: (a) the resistance across AB when switch S is open. (b) the resistance across AB when switch S is closed.

A resistance R is connected across a cell with a switch and a rheostat in series. A voltmeter is connected parallel across the cell. Current in the circuit is increased using the rheostat. (a) How will the voltmeter reading change? (increase / decrease / remain the same) (b) Justify your answer stated in (a) above.

The specific resistance of a wire depends on: (a) its length (b) the material of the wire (c) its cross-sectional area (d) its radius

When a current I flows through a wire of resistance R for time t then the electrical energy produced is given by: (a) I2Rt (b) IR2t (c) IRt (d) IRt2

The potential difference between the terminals of a cell in a closed circuit is called: (a) terminal voltage (b) electromotive force (c) voltage drop (d) none of these

In a closed circuit containing a bulb and a cell, the electromotive force (ε) and the terminal voltage (V) is related as. (Given I is current and r is internal resistance.) (a) V = ε + Ir (b) V = ε – Ir (c) V = ε ÷ Ir (d) V = ε × Ir

Choose the correct relation for e.m.f. (ε) and terminal voltage V: (a) ε = V [always] (b) V > ε [always] (c) V < ε [when the cell is in use] (d) None of these

In the given circuits Y and Z, the resistors, R₁ and R₂, are connected in : (a) series in both the circuits (b) parallel in both the circuits (c) parallel in Y and series in Z (d) series in Y and parallel in Z

Study the diagram: (a) Calculate the total resistance of the circuit. (b) Calculate the current drawn from the cell. (c) State whether the current through 10 Ω resistor is greater than, less than or equal to the current through the 12 Ω resistor.