________________
42. (a)
Satish K. Gupta, op. cit,. p. 30
"Concept of electric field
Consider that an electric charge q is present at some point in space. If we bring any other charge say q near the charge q, it will experience a force of attraction or repulsion due to the charge q. The force experienced by the charge q is said to be due to the electric field set up by the charge q.
The electric field of a charge is the space property by virtue of which the charge modifies the space around itself. As a result, if any other charge is brought in the space around the charge, it experiences electrostatic force.
Thus, electric field due to a charge is the space around the charge, in which any other charge is acted upon by an electrostatic force."
(b) Ibid., p.161- "The electric field is the space around an electric charge in which its effect can be experienced."
43. Ibid., p. 222
"Electric Current
"It is defined as the rate of flow of electric charge through any section of a wire. It is denoted by I. Then
I = total charge flowing / time taken
If charge q flows in a time t through any section of a wire, then
I
q/t
If n carriers of electricity, each having charge e, cross any section of the conductor in time t then
1 = ne/t
If charge dq flows through a wire in small time dt, then
I = dq/dt
The direction in which the positive charge will flow gives the direction of conventional current. Since the flow of current is attributed to flow of electrons, the direction of electronic current is opposite to that of conventional current.
Although, a direction is associated with electric current, yet it is a scalar quantity. The reason is that the laws of ordinary algebra are used to add electric current. The laws of vector algebra do not apply to the addition of electric currents.
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