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Answer

Similarities differences

Both are used to measure small length Instrument (a) is called micrometer screw gauge which can measure up to 0.01mm accurately

Both are used to measure length more accurately compared to metre ruler

Instrument (b) is called Vernier calipers which can measure up to 0.01cm accurately

Both instruments have two scale, main scale and vernier scale

Answer

When taking measurement:

The thimble is turned until the anvil and the spindle grip the object tight

The ratchet knob is then turned until a click sound is heard to ensure that suitable pressure is exerted onto the object.

Check the positive zero shown by instrument (b)

Actual reading = measurement reading positive zero error

Avoid parallex error while taking reading by positioning both eyes directly onto the scale.

Increase the accuracy of the reading by taking three reading at three different points of the glass rod and find its average.

Answer

Design Reason

Use thin hollow tube as capillary tube more obvious contraction and expansion of mercury when temperature changes.

bulb of thermometer which filled with mercury is small

Increase its sensitivity

Use mercury as the liquid Opaque (easily to read) Does not stick on the glass wall

Put the thermometer in pure melting ice and steam to obtain ice point and steam point.

The temperature scale is obtained by dividing the temperature between the ice point and the steam point into one hundred equal parts.

Each part of scale represents 1C

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Answer

The induced current in the alternator is bigger than the dynamo bicycle

The number of turns of the of coil in the alternator is more compared to dynamo bicycle.

The magnet used in the alternator is stronger than the dynamo

The speed of rotation of the alternator is faster than dynamo

The physics concept is the electromagnetic induction.

Current is produced in a conductor when there is a relative motion between the conductor and the magnetic field.

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Answer

Modification Reason Use slip rings to replace the commutator Make sure the coil turn in one direction

Use a.c supply with higher magnitude Increase the speed of rotation of motor

increase the number of turns in coil Increase the speed of rotation of motor Use stronger magnet Increase the speed of rotation of motor

Winding the coils on a soft iron core Increase the magnetic field strength

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Answer

Choose Reason

Type of lens Convex lens Magnified the object

Focal length Focal length of objective lens, fo is longer than eyepiece lens,fe

Objective lens is use to form an image at the focal point of eyepiece lens, so that the eyepiece can magnified the image form by the objective lens at infinity

Diameter of lens large More light entering the telescope to produce brighter and clearer image

Magnification, M = fo / fe

Large ratio Obtain bigger image

Choose T as objective lens and Q as eyepiece lens.

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Answer

Characteristic Reason

Resistivity Low Reduce power loss

Melting Point high High heat produced in the wire will not melt it

Density low lighter

Cost lower Save cost

Choose Y for the transmission cable because it has low resistivity, high melting point, low density and medium cost.