4.2.3. Electromotive force and potential difference
A subsection of Physics, 0625, through 4. Electricity and magnetism
Listing 10 of 96 questions
This question is about electric circuits. State the name of the instrument used to measure potential difference (p.d.) in an electric circuit. State the unit for the electromotive force (e.m.f.) of a battery. A student connects a circuit to determine the resistance of a wire. The current in the wire is 0.20 A when the potential difference across the wire is 6.4 V. Calculate the resistance of the wire. resistance = Ω The student has some wires of the same material as those in but of various lengths and thicknesses. He wants a wire with higher resistance than the wire in . State two ways of identifying a wire with a higher resistance by comparing its length and thickness with the wire in .
0625_w21_qp_31
THEORY
2021
Paper 3, Variant 1
View
A potential divider is made by connecting a light-dependent resistor (LDR) and a thermistor in series. shows the potential divider, a voltmeter and a direct current (d.c.) power supply connected into a circuit. V + – The voltmeter measures the potential difference (p.d.) across the LDR. Define potential difference (p.d.). The electromotive force (e.m.f.) of the supply is E. Describe how the p.d. across the thermistor can be determined using the reading on the voltmeter. The resistance of the LDR decreases and the resistance of the thermistor increases. State what has happened to the light intensity incident on the LDR and the temperature of the thermistor. intensity of incident light on LDR: temperature of thermistor: Explain what happens to the reading on the voltmeter.
0625_w24_qp_41
THEORY
2024
Paper 4, Variant 1
View
shows a circuit containing a battery of electromotive force (e.m.f.) 12 V and a heater of resistance 6.0 Ω. A 6.0 1 12 V State what is meant by electromotive force (e.m.f.). Calculate the current in the heater. current = State the name of the particles that flow through the heater. On , draw an arrow next to the heater symbol to show the direction of flow of these particles through the heater. Calculate the thermal energy produced in the heater in 10 minutes. thermal energy =
0625_s15_qp_32
THEORY
2015
Paper 3, Variant 2
View
A student investigates an electric circuit. shows the student’s circuit. A heater 6.0 V Describe the purpose of the variable resistor in . The student uses cells with an electromotive force (e.m.f.) of 1.5 V. Determine the number of cells needed for the 6.0 V battery in . number of cells needed = The student connects another component to measure the potential difference (p.d.) across the heater. On , draw the electrical symbol and connections for this component. The p.d. across the heater is 4.0 V. The current in the heater is 1.6 A. Calculate the energy transferred electrically by the heater in 40 s. energy transferred = J
0625_w23_qp_31
THEORY
2023
Paper 3, Variant 1
View
shows the circuit diagram for a flashlight . The electromotive force (e.m.f.) of the battery is 4.5 V. The circuit contains a 60 Ω fixed resistor. The current in the light-emitting diode (LED) is 0.020 A. Calculate the potential difference (p.d.) across the LED. p.d. = Explain why the LED does not light up if the battery is reversed. The chemical energy stored in the battery is 1050 J. Show that the flashlight operates for approximately 3 h. Calculate the total charge that flows through the LED in 3600 s. charge =
0625_w23_qp_42
THEORY
2023
Paper 4, Variant 2
View
Questions Discovered
96