Question

(a) Define electric current. What is the SI unit of electric current?
(b) One coulomb of charge flows through any cross - section of a conductor in \[1\] second? What is the current flowing through the conductor?
(c) Which instrument is used to measure electric current? How should it be connected in a circuit?
(d) What is the conventional direction of the flow of electric current?
How does it differ from the direction of flow of electrons?
(e) A flash of lightning carries \[10C\] of charge which flows for \[0.01s\]. What is the current? If the voltage is \[10MV\], what is the energy?

Answer 1

Hint: We need to know the basic definition of current and related formulas to solve the question. Also, we need to know how current is produced and its direction of flow. Also, we have to know how current and charge are related to each other and other formulas related to current.

Complete step by step solution:
A. We can define an electric current as a stream of charged particles (maybe electrons or ions) flowing through a conductor or space such as a metal wire.
The SI unit of electric current is ampere (A).
B. We know the definition of current tells us that it is the rate of flow of charge, thus here we are given one coulomb charge is flowing through a cross section in unit seconds. Thus, current is one ampere.
C. To measure the current through an electric circuit we use an ammeter. Note the fact that in a series connection, all the equipment receives the same current while for a parallel circuit we get equal voltage across all the appliances. Thus, if we need to measure current, we have to connect the ammeter in series with the circuit.
D. The conventional direction of flow of electric current is from the positive terminal of the battery to the negative terminal of the battery, through the external circuit. The direction of flow of electrons is just opposite to the direction of current, from the negative terminal of the battery to the positive terminal of the battery.
E. Given charge = \[10C\], time = \[0.01s\]. Thus, current I = \[\dfrac{Q}{t} = \dfrac{{10}}{{0.01}} = 1000A\] .
Now it’s given that voltage is \[10MV\], thus power = \[VI\]= \[10_{}^4MW\]
Now work= power \[ \times \] time = \[10_{}^4MW\]\[ \times \] \[0.01s\] = \[100MJ\].

Note: Use the definition and simple formulas of current to solve the problems. Remember how we find the direction of current and how it is related to electron flow direction. Keep in mind the units while solving the sums.