Physics Stpm Sem 2 Definition

Coulomb’s law states that the magnitude of electrostatic force between two points charges is directly proportional to the product of their charges and inversely proportional to the square of their distance apart. Electric field strength at a point in an electric field is defined as the electric force per unit charge acting on a small positive test charge which is placed at a point. Electrical potential at a point in an electric field is defined as the work done in moving a unit positive charge from infinity to a point. Gauss’ Law states that the total electric flux passing through a closed surface is equal to ∑Q/ε, where ∑Q is the total charge inside the closed surface. Ø=∑Q/ε The electric potential difference between two points is defined as the work done in moving a unit positive charge between the two points. The electric field passes through the lower surface of the cuboid only and therefore the total electric flux passing through the Gaussian surface given by, Ø =EA The electric potential different between two points is defined as the work done in moving a unit positive charge between the two points. Electric potential at a point in an electric field is defined as the work done in moving a unit positive charge from infinity to a point. Capacitance of a capacitor is defined as the ratio of the charge stored on either plate to the potential difference across the plates. The time constant of a discharging circuit is defined as the time taken for the charge stored on a capacitor to decrease to (1/e)(37%) of its initial value. The time constant of a charging circuit is defined as the time taken for the charge stored on a capacitor to increase to (1-1/e)(63%) of its initial value. Drift velocity is the average velocity of the free electrons in the direction opposite to the direction of the electric field applied. (Vd ~10-4) Electrical resistance of a conductor is a measure of its opposition to current flow and it is defined as the ratio of potential difference across a conductor to the current passing through it. Ohm’s law states that the magnitude of electric current passing through a metallic conductor is directly proportional to the potential difference applied provided the temperature and other physical factors of the conductor remains unchanged. Electrical energy is defined as a work done in moving electric charge across an electrical component in a circuit. Electrical power is defined as the rate of change of electrical energy

The emf of an electrical source is defined as the amount of electrical energy generated when 1 coulomb of electric charge is delivered by the battery around a complete circuit. Kirchhoff’s first law states that the total current at any junction of a circuit is always zero. Kirchhoff’s second law states that, for any closed loop in a circuit, the total emf is always equal to the potential different across the loop. Magnetic field is a region in space where magnetic force is experienced by a moving charge or magnetic substances. The magnetic flux density, B at a point is defined as the magnetic force per unit charge per unit velocity acting on a positive charge which is moving in a direction perpendicular to the magnetic field. B can be also derived as the magnetic force per unit current per unit length acting on a current carrying conductor which is placed perpendicularly to the magnetic force. Ampere’s law states that for any closed path, the sum of the products between element length, Δl and B (magnetic field along Δl) is always equal to µI. One ampere is defined as the value of steady current when flowing in two infinitely long and thin parallel wires which are separated by 1m in vacuum will produce a mutual magnetic force per unit length of 2X10-7 Nm-1. Faraday’s law states that the magnitude of emf induced in a circuit is directly proportional to the rate of change of magnetic flux linked to the surface. Lenz’ law states that the induced current in the circuit will always flow in the direction such as to oppose the magnetic flux change producing the current. The self-inductance of an inductor is defined as the ration of magnetic flux linking the inductor to the current passing through it or the ration of back emf induced in the inductor to the rate of change of current flowing in the inductor. A self inductance of 1H is numerically equal to 1V emf induced in an inductor when the rate of current flowing is 1As-1. The mutual inductance of a pair of coils is defined as the ratio of magnetic flux linkage in the second coil to the current flowing in the first coil or the ratio of emf induced in the second coil to the rate of change of current flowing in the first coil. Alternating current is a current that flow to and fro in a circuit periodically. Irms is an effective value for an AC current, it is defined as the value of steasy current which will dissipate electrical energy into heat as the same rate as the AC if both currents pass through the same resistor.