An electrical circuit is constructed to investigate how a variable resistor (rheostat) affects the current in a circuit containing a filament bulb.
State how an ammeter and a voltmeter must be connected relative to the bulb to measure its resistance.
At a certain setting, the potential difference (p.d.) across the bulb is 7.5 V7.5\text{ V}7.5 V and the current is 0.25 A0.25\text{ A}0.25 A. Calculate the resistance of the bulb.
The variable resistor consists of a coil of resistance wire, a metal bar above it, and a sliding contact. The circuit connections are made at the left-hand end of the coil of resistance wire and the right-hand end of the metal bar.
State and explain the effect on the current in the circuit when the sliding contact is moved from the far right to the far left.
452 exam-style questions on CIE IGCSE Physics 4.2 Electrical quantities, covering 4.2.1a Positive and negative charge, 4.2.1b Charging by friction and detecting charge, 4.2.1c Electrical conductors and insulators, 4.2.1d Electric fields and electric field patterns, 4.2.2a Electric current, charge and measuring current, 4.2.2b Conduction in metals and the direction of current, 4.2.2c Direct current and alternating current, 4.2.3a Electromotive force, 4.2.3b Potential difference and voltmeters, 4.2.4a Resistance, 4.2.4b Resistance of a metallic wire, 4.2.4c Current–voltage graphs, and 4.2.5 Electrical energy and electrical power. Each one has a worked solution and a mark scheme showing where the marks go.