Thermal and Electromagnetism

Question 1

Coloumb’s law

Answer 1

Coulomb’s law states that the electric force acting between any two point charges is directly proportional to the product of the charges and inversely proportional to the square of their distance apart and the direction of the force is along the line joining the two point charges in free space.

Question 2

Electric field strength

Answer 2

Electric field strength at a point is defined as the electric force exerted per unit positive charge on a small positive stationary test charge placed at that point in the electric field.

Question 3

Electric potential energy

Answer 3

Electric potential energy of a system of charges is defined as the work done by an external agent in bringing the charges from infinity to their positions in the system, without producing any acceleration.

Question 4

Electric potential

Answer 4

Electric potential at a point in an electric field is defined as the work done per unit positive charge by an external agent in bringing a small positive test charge from infinity to that point, without producing any acceleration.

Question 5

Current

Answer 5

The current is the charge per unit time (rate of charge) flowing through a cross-sectional area.

Question 6

Resistance

Answer 6

The resistance of a conductor is defined as the ratio of potential difference across the conductor and current flowing through the conductor.

Question 7

Ohm’s law

Answer 7

Ohm’s law states that the current flowing through a conductor is directly proportional to the potential difference applied across the conductor provided that the physical conditions (such as temperature, stress etc) remain constant.

Question 8

Resistivity

Answer 8

Resistivity is an electrical property of the material and its value gives the electrical resistance of a conductor of unit cross-sectional area and unit length, made from that material.

Question 9

Potential difference

Answer 9

The electric potential difference between two points in a circuit is the amount of electrical energy converted to other forms of energy per unit charge passing through them.

Question 10

Electromotive force (emf)

Answer 10

Electromotive force is the amount of non-electrical energy converted into electrical energy per unit charge passing through the terminals of the cell (source).

Question 11

Root mean square (rms) of A.C.

Answer 11

Root mean square (r.m.s) of an alternating current is defined as the value of the steady direct current which would dissipate heat at the same average rate in a given resistor as the A.C..

Question 12

Peak value of A.C.

Answer 12

Peak value of an a.c.(or amplitude) of alternating current is the maximum value of the current in a periodic cycle.

Question 12

Rectification

Answer 12

Rectification is the process of converting alternating current to a unidirectional current.

Question 13

Magnetic Flux Density

Answer 13

The magnetic flux density at a given region of space is defined as the force per unit length acting on a straight, current-carrying conductor, carrying unit current and placed at right angles to this external magnetic field.

Question 14

Magnetic Flux

Answer 14

The magnetic flux is defined as the product of an area and the component of the magnetic flux density perpendicular to that area.

Question 15

Faraday’s Law

Answer 15

Faraday’s law states that the magnitude of the induced e.m.f. in a conductor is directly proportional to the rate of change of magnetic flux linkage experienced by the conductor.

Question 16

Lenz’s Law

Answer 16

Lenz’s law states that the direction/polarity of the induced e.m.f. is such that it produces effects that oppose the change producing it.

Question 17

Specific heat capacity

Answer 17

Specific heat capacity of a substance is defined as the quantity of heat (thermal energy) required to produce a unit temperature rise in a unit mass of the substance without a change of phase of the substance.

Question 18

Specific latent heat of vaporisation/fusion

Answer 18

Specific latent heat of vaporisation of a substance is defined as the quantity of heat (thermal energy) required to change unit mass of the substance from the liquid state to its gaseous state/the solid state to the liquid state and vice versa without a change in temperature of the substance.

Question 19

Internal energy

Answer 19

The internal energy U of a system is the sum of the microscopic random distribution of potential (do not say for ideal gas) and kinetic energies of the atoms or molecules (particles) in the system.

Question 20

The First Law of Thermodynamics

Answer 20

The First Law of Thermodynamics states that the increase in internal energy of a system is the sum of the heat supplied to the system and the work done on the system.