Measurement Techniques

What could describe the time-base of a cathode-ray oscilloscope (CRO)?

Options

A   the frequency per division on the screen
B   the number of divisions on the screen per unit frequency
C   the number of divisions on the screen per unit time
D   the time per division on the screen

In an experiment, a student uses a microphone and a cathode-ray oscilloscope (CRO) to analyse a sound wave. The diagram shows the trace on the screen of the CRO.

The student is expecting a sinusoidal waveform to be shown on the screen.

Which changes should the student make to the time-base and the $y$-gain of the CRO so that the screen shows a continuous trace for one complete cycle of the waveform?

Options

A cathode-ray oscilloscope (CRO) is used to determine the frequency of a sound wave.
The diagram shows the waveform on the screen.
The time-base setting is $5.0\text{ ms div}^{-1}$.

What is the best estimate of the frequency of the sound wave?

Options

A   $50\text{ Hz}$
B   $71\text{ Hz}$
C   $100\text{ Hz}$
D   $143\text{ Hz}$

A micrometer screw gauge is used to measure the diameter of a copper wire.

The reading with the wire in position is shown in diagram 1. The wire is removed and the jaws of the micrometer are closed. The new reading is shown in diagram 2.

What is the diameter of the wire?

Options

A   $1.95\ \text{mm}$
B   $2.45\ \text{mm}$
C   $2.59\ \text{mm}$
D   $2.73\ \text{mm}$

A signal of frequency $25\ \text{Hz}$ is displayed on the screen of a cathode-ray oscilloscope.

What is the time-base setting?

Options

A   $10\ \text{ms cm}^{-1}$
B   $20\ \text{ms cm}^{-1}$
C   $25\ \text{ms cm}^{-1}$
D   $40\ \text{ms cm}^{-1}$

A micrometer screw gauge is used to measure the diameter of a wire.

The reading on the micrometer with the jaws closed is $(-0.05 \pm 0.02)\ \text{mm}$.

The reading with the wire in position between the two jaws is $(+1.03 \pm 0.02)\ \text{mm}$.

What is the diameter of the wire?

Options

A   $(0.98 \pm 0.02)\ \text{mm}$
B   $(1.08 \pm 0.02)\ \text{mm}$
C   $(0.98 \pm 0.04)\ \text{mm}$
D   $(1.08 \pm 0.04)\ \text{mm}$

An analogue ammeter with a range of $0$–$250\text{ mA}$ is connected into an electrical circuit. The diagram shows the ammeter’s display.

What is the reading on the ammeter?

Options

A   $76\text{ mA}$
B   $165\text{ mA}$
C   $183\text{ mA}$
D   $190\text{ mA}$

The diagram shows two readings on a micrometer.

What is the difference between the two readings?

Options

A   $10.34\text{ mm}$
B   $11.84\text{ mm}$
C   $12.34\text{ mm}$
D   $12.84\text{ mm}$

A paperback book contains 210 sheets of paper (pages). Its thickness is measured with a ruler, as shown.

What is the average thickness of one sheet of the paper in the book?

Options

A   0.013 mm
B   0.017 mm
C   0.13 mm
D   0.17 mm

A transmitter emits a pulse of electromagnetic waves towards a reflector. The pulse is reflected and returns to the transmitter.

A detector is located at the transmitter. The emitted pulse and the reflected pulse are displayed on a cathode-ray oscilloscope (CRO) as shown.

The pulse takes $6.3\,\mu\text{s}$ to travel from the transmitter to the reflector.

What is the time-base setting of the CRO?

Options

A   $2.1\,\mu\text{s cm}^{-1}$
B   $3.2\,\mu\text{s cm}^{-1}$
C   $4.2\,\mu\text{s cm}^{-1}$
D   $6.3\,\mu\text{s cm}^{-1}$