A student investigates the brightness of a lamp. Plan an experiment to investigate how the intensity (brightness) of the light produced by the lamp is affected by the current in the lamp. The apparatus available includes: - a lamp and power supply - a light meter which measures the intensity of light arriving at it - an ammeter - a variable resistor. You are not required to do this experiment. In your plan, you should: - complete the circuit diagram in Fig. 4.1 to show the variable resistor connected to control the current in the lamp - $$$\quad$$$ state the key variables to be kept constant - explain briefly how to do the experiment - draw a table with column headings, to show how to display the readings (you are not required to enter any readings in the table) - $$$\quad$$$ explain how to use the readings to reach a conclusion.

Physics

IGCSE&ALevel

CAIE

Exam No：0625_w23_qp_53 Year：2023 Question No：4

Answer:

Knowledge points:

4.2.1.1 State that there are positive and negative charges

4.2.1.10 Give an account of charging by induction

4.2.1.11 Recall and use a simple electron model to distinguish between conductors and insulators

4.2.1.2 State that unlike charges attract and that like charges repel

4.2.1.3 Describe simple experiments to show the production and detection of electrostatic charges

4.2.1.4 State that charging a body involves the addition or removal of electrons

4.2.1.5 Distinguish between electrical conductors and insulators and give typical examples

4.2.1.6 State that charge is measured in coulombs

4.2.1.7 State that the direction of an electric field at a point is the direction of the force on a positive charge at that point

4.2.1.8 Describe an electric field as a region in which an electric charge experiences a force

4.2.1.9 Describe simple field patterns, including the field around a point charge, the field around a charged conducting sphere and the field between two parallel plates (not including end effects)

4.2.2.1 State that current is related to the flow of charge

4.2.2.2 Use and describe the use of an ammeter, both analogue and digital

4.2.2.3 State that current in metals is due to a flow of electrons

4.2.2.4 Show understanding that a current is a rate of flow of charge and recall and use the equation I = Q / t

4.2.2.5 Distinguish between the direction of flow of electrons and conventional current

4.2.3.1 State that the electromotive force (e.m.f.) of an electrical source of energy is measured in volts

4.2.3.2 Show understanding that e.m.f. is defined in terms of energy supplied by a source in driving charge round a complete circuit

4.2.4.1 State that the potential difference (p.d.) across a circuit component is measured in volts

4.2.4.2 Use and describe the use of a voltmeter, both analogue and digital

4.2.4.3 Recall that 1 V is equivalent to 1 J / C

4.2.5.1 State that resistance = p.d. / current and understand qualitatively how changes in p.d. or resistance affect current

4.2.5.2 Recall and use the equation R =V / I

4.2.5.3 Describe an experiment to determine resistance using a voltmeter and an ammeter

4.2.5.4 Relate (without calculation) the resistance of a wire to its length and to its diameter

4.2.5.5 Sketch and explain the current–voltage characteristic of an ohmic resistor and a filament lamp

4.2.5.6 Recall and use quantitatively the proportionality between resistance and length, and the inverse proportionality between resistance and cross- sectional area of a wire

4.2.6.1 Understand that electric circuits transfer energy from the battery or power source to the circuit components then into the surroundings

4.2.6.2 Recall and use the equations P=IV and E=IVt

4.3.1.1 Draw and interpret circuit diagrams containing sources, switches, resistors (fixed and variable), heaters, thermistors, light-dependent resistors, lamps, ammeters, voltmeters, galvanometers, magnetising coils, transformers, bells, fuses and relays

4.3.1.2 Draw and interpret circuit diagrams containing diodes

4.3.2.1 Understand that the current at every point in a series circuit is the same

4.3.2.2 Give the combined resistance of two or more resistors in series

4.3.2.3 State that, for a parallel circuit, the current from the source is larger than the current in each branch

4.3.2.4 State that the combined resistance of two resistors in parallel is less than that of either resistor by itself

4.3.2.5 State the advantages of connecting lamps in parallel in a lighting circuit

4.3.2.6 Calculate the combined e.m.f. of several sources in series

4.3.2.7 Recall and use the fact that the sum of the p.d.s across the components in a series circuit is equal to the total p.d. across the supply

4.3.2.8 Recall and use the fact that the current from the source is the sum of the currents in the separate branches of a parallel circuit

4.3.2.9 Calculate the effective resistance of two resistors in parallel

4.3.3.1 Describe the action of a variable potential divider (potentiometer)

4.3.3.2 Describe the action of thermistors and light- dependent resistors and show understanding of their use as input transducers

4.3.3.3 Describe the action of a relay and show understanding of its use in switching circuits

4.3.3.4 Describe the action of a diode and show understanding of its use as a rectifier

4.3.3.5 Recognise and show understanding of circuits operating as light-sensitive switches and temperature-operated alarms (to include the use of a relay)

Answer:

Knowledge points:

Solution:

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