· Damping is the effect that causes energy and amplitude of a wave to be decreasing with time.
· Sound is a mechanical wave that propagates through matter as a longitudinal wave. The normal hearing range is 20 Hz to 20 000 Hz. Sound which is above the hearing range is known as ultrasound and that below the hearing range is known as infrasound.
1. Electromagnetic waves are waves which consists of an electric charge and a magnetic field oscillating at right angles to each other.
1. After diffraction, the wavelength, speed and frequency remain the same. The direction of the diffracted waves depends on the size of the aperture or obstacle.
MOVEMENT OF CURRENTS AND ELECTRONS
· Current always travels from the positive terminal to the negative terminal of the battery. However, electrons always travels from the negative terminal to the positive terminal of the battery.
· Electrical appliances which depend on the heating effect of current have higher power.
· Superconductors will occur when the resistance of certain metals become zero at very low temperature that nearly absolute zero.
· Ohm’s law states the electric current, I moving a through a conductor is directly proportional to the potential difference or voltage across the ends of the conductor, if the temperature and other physical factors remains constant.
STRENGTH OF THE MAGNETIC FIELD
· The strength of the magnetic field due to a straight current-carrying wire is
a. directly proportional to the magnitude of current
b. inversely proportional to the distance from the wire.
SOFT IRON CORE
· The soft iron core is used frequently in electromagnets for two reasons:
a. It produces a stronger magnetic field by concentrating the magnetic field lines.
b. It can be magnetized and demagnetized easily thus reducing loss of energy.
· Electromagnetic induction is known as the production of an electric current by the changing of magnetic field.
· Lenz’s law states that the direction of the induced current is such that the change producing it will be opposed.
· Doping is adding a small number of trivalent or pentavalent atoms into pure semiconductors to increase its conductivity. Doping produce p-type and n-type semiconductors.
· The rate of thermionic emission increases if
a. the surface area of the metal increases
b. the temperature of the metal increases
c. different type of metals are used
d. the metals are coated with barium oxide or strontium oxide.
· Rectification is a process to convert an alternating current into a direct current by using diode.
TRANSISTOR AS AN AMPLIFIER
· A transistor can be used to amplify current. This is because a small change in base current causes a large change in collector current.
· Radioactivity is the spontaneous and random emission of radioactive rays from unstable radioactive materials after which they become more stable.
· Nuclear fission is the splitting of a nucleus with big mass into two or more smaller nuclides with the release of energy.
· Nuclear fusion is the combination of small atoms into a larger atom and with the release of heat.
· Radioactive decay is a process where an unstable nucleus becomes a more stable nucleus by emitting radiations.
· In radioactive decay, one element changes into another in a process called transmission. The mass of daughter particles is less than that of the parent particle. This difference in mass is called the mass defect or mass loss.