Use of Measuring Instruments & Electrical Equipment (OCR A Level Physics): Flashcards

Determining the volume of a liquid, checking that two objects are aligned, and reading the temperature from a thermometer (any two).

A vernier scale allows accurate interpolation between the smallest divisions on a main scale.

False.

Parallax error is minimised only by reading the scale perpendicular to the line of sight (at eye level), not from any consistent angle.

It directly measures the weight, W. The mass is then calculated using .

An instrument capable of measuring voltage, current and resistance, so it can be used as a voltmeter, ammeter or ohmmeter.

Standard digital ammeters and voltmeters struggle to measure very small currents/voltages (of the order of μA or mA), whereas a multimeter can measure a much greater range of readings.

The fuse inside the multimeter blows and must be replaced.

Before setting the dial on a multimeter, the correct range of currents or voltages should be estimated.

False.

A multimeter should be turned off after use so that its battery does not run out.

A digital switch-type sensor consisting of an infrared transmitter and receiver; a timer starts or stops when the beam between them is obstructed.

0.01 s

Human reaction time (about 0.25 s), delay in the mechanism of older stopwatches, accidentally pressing the start/stop button too many times, and consistently starting the stopwatch too early or too late (any three).

Using , where distance is the known separation between the two light gates and time is the interval between the object passing each one, assuming the object is not accelerating.

A light gate is more accurate than a stopwatch because it removes errors caused by human reaction time.

False.

If the distance between two light gates is known, the time interval between an object passing through both can be used to calculate its speed.

A tool used for measuring small widths, thicknesses or diameters, with a resolution of 0.01 mm.

To reduce the chance of overtightening the object being measured, which could deform it or cause zero errors.

Two decimal places (e.g. 1.40 mm, not just 1.4 mm).

A tool with a sliding vernier scale used to measure diameters, thicknesses, lengths and depths, typically with a resolution of 0.1 mm.

The micrometer has a smaller measuring range than the vernier caliper, but better accuracy due to its finer resolution.

False.

The micrometer has better accuracy, due to its finer resolution, despite having a smaller measuring range than the vernier caliper.

The vernier caliper, because it does not require rotating a thimble, unlike the micrometer.

In series, so that the full current flowing through the circuit passes through it.

In parallel with the component whose potential difference is being measured.

A component that can only be connected in a circuit in one direction; connecting it the wrong way round will cause it to not work, work incorrectly, or break.

Cells/batteries/power supplies, diodes, LEDs, and electrolytic capacitors (any three).

On an LED, the longer leg is the positive (anode) pin.

False.

A lamp is non-polarised and will light up regardless of the direction it is connected.

A switch allows the current path to be changed between the two configurations.

An electronic test instrument used to create repeating or non-repeating waveforms of adjustable shape and amplitude, often used to generate signals for display on an oscilloscope.

A laboratory instrument used to display, measure and analyse waveforms of electrical circuits; it can be used as both an a.c. and d.c. voltmeter.

The x-axis represents time and the y-axis represents voltage (or y-gain).

An a.c. voltage is displayed as a transverse wave; a d.c. voltage is displayed as a horizontal line at the relevant voltage.

The oscilloscope setting that determines how many seconds each division represents (measured in s div^-1 or s cm^-1); it is used to determine the period of the wave.

The voltage-gain (sensitivity) setting controls the vertical deflection, or amplitude, of the wave displayed on an oscilloscope.

The peak voltage (V₀) is the maximum vertical displacement measured from the time axis. The peak-to-peak voltage is the vertical displacement between the minimum and maximum values of voltage.

False.

When the time-base is switched off, only a vertical line at the relevant amplitude is seen; a wave only appears across the screen when the time-base is switched on.

A class 2 laser is one with a power output of less than 1 mW; the only laser class permitted for use in schools.

A class 4 laser is one with a power output of more than 500 mW; powerful enough to cause instant blindness and damage to the skin.

A laser produces coherent, monochromatic light, giving a sharper, brighter interference pattern with greater contrast between bright and dark fringes than a lamp, which has low intensity and emits light of all wavelengths.

There will be a large error in the measurement of the fringe width.

Never look directly at a laser or its reflection.

Any three of:

• Never look directly at a laser or its reflection

• Don't shine the laser towards a person

• Don't allow the beam to reflect from shiny surfaces into someone's eyes

• Wear laser safety goggles

• Place a 'laser on' warning light outside the room

• Stand behind the laser

False.

Class 4 lasers have a much higher power output (more than 500 mW) than class 2 lasers (less than 1 mW) and are far more hazardous.

An electronic device that automatically monitors and records environmental parameters (such as temperature, pressure, voltage or current) over time, using sensors and a computer chip to store the data.

Processing data collected from a physics experiment into software or a spreadsheet to generate graphs and charts, which can then be exported to a scientific report.

Any three of: readings taken with higher accuracy; reduction of human error; readings taken over a long period of time; readings taken in a very short period of time; reduction in safety risks with extreme conditions.

Time can be sped up to predict the future outcome of an experiment.

A data logger contains multiple sensors to receive information, and a computer chip to store it.

False.

A data logger can monitor and record a range of environmental parameters, including temperature, pressure, voltage and current.

Radiation with enough energy to ionise atoms, including alpha, beta and high-energy electromagnetic radiation such as X-rays, gamma rays and UV.

The amount of radiation (number of decays) given off by an isotope each second, measured in becquerels (Bq). An activity of one Bq means one decay per second.

It detects the presence of ions created by radiation entering the tube. Connecting the tube to a counter allows the amount of radiation to be determined.

Any two of: workers are monitored (e.g. with a photographic film badge) to check radiation exposure, with strict limits set; limits on the time spent using radioactive materials; barriers placed between worker and source to absorb radiation; leaving the room during procedures such as X-rays.

The universal radiation hazard symbol is important because it means people who speak any language can still understand its meaning.

False.

Doctors will leave the room during certain procedures, including X-rays, in order to minimise their exposure to ionising radiation.