Physics Quiz 4

A dynamo is a device for converting mechanical energy into electrical energy. In a dynamo, the mechanical energy of rotation is converted into electrical energy in the form of a current in the armature.

Energy is transferred from the sun to Earth via electromagnetic waves, or radiation. Radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium.

A parabolic concave mirror is used in torches and car headlamps as reflectors. This type of mirror is capable of directing the light at a particular point as they have converging power. These mirrors provide clear visibility.

Radiocarbon Dating (carbon-14 dating) is used to estimate the age of fossils. It is a method of age determination that depends upon the decay to nitrogen of radiocarbon (carbon-14).

Communication satellites are used to receive and retransmit communication signals. A satellite is basically a self-contained communications system with the ability to receive signals from Earth and to retransmit those signals back with the use of a transponder—an integrated receiver and transmitter of radio signals.

White and black combination of colours is the most convenient during day and night time. Black text on a white background is best, since the colour properties and light are best suited for the human eye. That's because white reflects every wavelength in the colour spectrum.

A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. It swings back and forth in a precise time interval. A pendulum clock takes 1 second to move from one extreme to the other extreme, so its time period is 2 seconds.

If the force is held constant the pressure is inversely proportional to the area (Pressure = force/area). Here area of the nail is much greater than the area of the needle. Thus, needle exerts more pressure than nail on the balloon.

The apparent weight of a man in a lift is less than the real weight when the lift is going down with an acceleration. When a lift accelerates upwards, the apparent weight of the person inside it increases; and when a lift accelerates downwards, the apparent weight of the person inside it decreases.

A bolometer is an instrument for measuring radiation by means of the rise in temperature of a blackened metal strip in one of the arms of a resistance bridge.