Simple circuits (P3.2) | OCR GCSE Physics A (Gateway Science) — Higher (J249)

P3.2 Simple circuits

Summary Electrical currents depend on the movement of charge and the interaction of electrostatic fields. Electrical current, potential difference and resistance are all discussed in this section. The relationship between them is considered and learners will investigate this using circuits. Underlying knowledge and understanding Learners should have been introduced to the measurement of conventional current and potential difference in circuits. They will have an understanding of how to assemble series and parallel circuits and of how they differ with respect to conventional current and potential difference. Learners are expected to have an

awareness of the relationship between potential difference, current and resistance and the units in which they are measured. Common misconceptions Learners find the concept of potential difference very difficult to grasp. They find it difficult to understand the behaviour of charge in circuits and through components and how this relates to energy or work done within a circuit.

Reference	Mathematical learning outcomes	Mathematical skills
$PM3.2i$	$potential difference (V) = current (A) \times resistance (Ω$

Learning outcomes	To include	Maths	Working scientifically	Practical suggestions
$P3.2a describe the differences between series and parallel circuits$	$positioning of measuring instruments in circuits and descriptions of the behaviour of energy, current and potential difference$		$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Building of circuits to measure potential difference and current in both series and parallel circuits. (PAG P7)$
$P3.2b represent d.c. circuits with the conventions of positive and negative terminals, and the symbols that represent common circuit elements$	$cells, power supply, diodes, LDRs, NTC thermistors, filament lamps, ammeter, voltmeter, fixed and variable resistors and switch$		$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Building circuits from diagrams. (PAG P7)$
$P3.2c recall that current, I, depends on both resistance, R, and potential difference, V, and the units in which these are measured$	$the definition of potential difference$		$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Recording of p.d. across and current through different components and calculate resistances. (PAG P6)$
$P3.2d recall and apply the relationship between I, R and V, and that for some resistors the value of R remains constant but that in others it can change as the current changes$		$M1a, M2a, M3a, M3b, M3c, M3d$	$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Investigation of resistance in a wire. (PAG P6) Investigation of the effect of length on resistance in a wire. (PAG P7)$
$P3.2e explain that for some resistors the value of R remains constant but that in others it can change as the current changes$
$P3.2f explain the design and use of circuits to explore such effects$	$components such as wire of varying resistance, filament lamps, diodes, NTC thermistors and LDRs$			$Building circuits and measurement of current and potential difference.$
$P3.2g use graphs to explore whether circuit elements are linear or non-linear$		$M4c, M4d$	$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Investigation of I-V characteristics of circuit elements. (PAG P6)$
$P3.2h use graphs and relate the curves produced to the function and properties of circuit elements$	$components such as wire of varying resistance, filament lamps, diodes, NTC thermistors and LDRs$	$M4c, M4d$	$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Use of wires, filament lamps, diodes, in simple circuits. Alter p.d. and keep current same using variable resistor. Record and plot results. (PAG P6)$
$P3.2i explain why, if two resistors are in series the net resistance is increased, whereas with two in parallel the net resistance is decreased (qualitative explanation only)$		$M1c$	$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Investigation of the brightness of bulbs in series and parallel. (PAG P7)$
$P3.2j calculate the currents, potential differences and resistances in d.c. series and parallel circuits$	$components such as wire of varying resistance, filament lamps, diodes, NTC thermistors and LDRs$	$M1a, M2a, M3a, M3b, M3c, M3d$	$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d$	$Investigation of resistance of a thermistor in a beaker of water being heated. (PAG P6) Investigation of resistance of an LDR with exposure to different light intensities. (PAG P6) Investigation of how the power of a photocell depends on its surface area and its distance from the light source. (PAG P6)$
$P3.2k explain the design and use of d.c. circuits for measurement and testing purposes$
$P3.2l explain how the power transfer in any circuit device is related to the potential difference across it and the current, and to the energy changes over a given time$
$P3.2m apply the equations relating potential difference, current, quantity of charge, resistance, power, energy, and time, and solve problems for circuits which include resistors in series, using the concept of equivalent resistance$		$M1c, M3b, M3c, M3d$

Learning outcomes

To include

Maths

Working scientifically

Practical suggestions

P3.2a describe the differences between series and parallel circuits

positioning of measuring instruments in circuits and descriptions of the behaviour of energy, current and potential difference

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Building of circuits to measure potential difference and current in both series and parallel circuits. (PAG P7)

P3.2b represent d.c. circuits with the conventions of positive and negative terminals, and the symbols that represent common circuit elements

cells, power supply, diodes, LDRs, NTC thermistors, filament lamps, ammeter, voltmeter, fixed and variable resistors and switch

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Building circuits from diagrams. (PAG P7)

P3.2c recall that current, I, depends on both resistance, R, and potential difference, V, and the units in which these are measured

the definition of potential difference

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Recording of p.d. across and current through different components and calculate resistances. (PAG P6)

P3.2d recall and apply the relationship between I, R and V, and that for some resistors the value of R remains constant but that in others it can change as the current changes

M1a, M2a, M3a, M3b, M3c, M3d

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Investigation of resistance in a wire. (PAG P6) Investigation of the effect of length on resistance in a wire. (PAG P7)

P3.2e explain that for some resistors the value of R remains constant but that in others it can change as the current changes

P3.2f explain the design and use of circuits to explore such effects

components such as wire of varying resistance, filament lamps, diodes, NTC thermistors and LDRs

Building circuits and measurement of current and potential difference.

P3.2g use graphs to explore whether circuit elements are linear or non-linear

M4c, M4d

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Investigation of I-V characteristics of circuit elements. (PAG P6)

P3.2h use graphs and relate the curves produced to the function and properties of circuit elements

components such as wire of varying resistance, filament lamps, diodes, NTC thermistors and LDRs

M4c, M4d

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Use of wires, filament lamps, diodes, in simple circuits. Alter p.d. and keep current same using variable resistor. Record and plot results. (PAG P6)

P3.2i explain why, if two resistors are in series the net resistance is increased, whereas with two in parallel the net resistance is decreased (qualitative explanation only)

M1c

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Investigation of the brightness of bulbs in series and parallel. (PAG P7)

P3.2j calculate the currents, potential differences and resistances in d.c. series and parallel circuits

components such as wire of varying resistance, filament lamps, diodes, NTC thermistors and LDRs

M1a, M2a, M3a, M3b, M3c, M3d

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS1.4a, WS2a, WS2b, WS2c, WS2d

Investigation of resistance of a thermistor in a beaker of water being heated. (PAG P6) Investigation of resistance of an LDR with exposure to different light intensities. (PAG P6) Investigation of how the power of a photocell depends on its surface area and its distance from the light source. (PAG P6)

P3.2k explain the design and use of d.c. circuits for measurement and testing purposes

P3.2l explain how the power transfer in any circuit device is related to the potential difference across it and the current, and to the energy changes over a given time

P3.2m apply the equations relating potential difference, current, quantity of charge, resistance, power, energy, and time, and solve problems for circuits which include resistors in series, using the concept of equivalent resistance

M1c, M3b, M3c, M3d

Simple circuits

Next Steps

Learning Objectives