Edexcel IGCSE Physics Observations and Variables

Practise Edexcel IGCSE Physics observations, measurements and variables by reading instruments, presenting data and identifying investigation variables.

Exam points

Choose or describe accurate measurement methods using suitable apparatus and reading technique.
Draw or complete a results table with correct headings, quantities and units.
Identify independent, dependent and control variables from an investigation method.

Covered syllabus points

Precise observations and measurements Independent, dependent and control variables

[Maximum number: 6]

Diagram 1 shows the apparatus a student uses to investigate the bending of a wooden strip.

Part of the wooden strip is clamped to a table.
A load is fixed to the free end of the wooden strip, causing it to bend.

Diagram 1

The free end of the wooden strip is positioned a length, L , beyond the edge of the table, as shown in diagram 1.

The weight of the load causes the end of the wooden strip to move down through a height, h.

A student investigates how the length, L , affects the height, h .

(a)

This is the student's method for the investigation.
- clamp the wooden strip so that $\mathrm{L}=20 \mathrm{~cm}$
- fix the load to the end of the wooden strip, as shown in diagram 1
- measure the height, h

The student repeats this method for different values of L.

[ 6 ]

(i)

Give the independent and dependent variables in the investigation.
independent variable
dependent variable

[ 2 ]

(ii)

Give two control variables in the investigation.

1

2

[ 2 ]

(iii)

Suggest how the student could accurately measure the height, h .

[ 2 ]

[Maximum number: 2]

A student uses this apparatus to investigate how the efficiency of an electric motor varies with its input voltage.

Figure for Question Observations, measurements and variables question 2 — Edexcel IGCSE Physics

This is the student's method.
- connect the electric motor to a d.c. power supply and a joulemeter
- attach a 1.0 kg mass to the electric motor using a length of string
- set the voltage of the power supply to 10 V and switch on the power supply
- switch off the power supply when the mass has been lifted through a distance of 50 cm
- record the input energy to the motor from the joulemeter
- calculate the energy transferred to the gravitational store of the mass
- calculate the efficiency of the motor

The student repeats this process, setting the power supply to a different voltage each time.

Give two control variables for the investigation.

1

2

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Covered syllabus points

Observations, measurements and variables question 1

Question (a)

Question (i)

Question (ii)

Question (iii)

Observations, measurements and variables question 2