Objective Questions on Electric Current

1. The flow of electric current in solids is due to

All electric currents consist of charges in motion. The charge is carried entirely by electrons. Electrons are free to move from atom to atom that enables the electric current to flow in a solid conductor.

2. Ampere second could be the unit of

A unit of electrical charge is equal to the amount of charge that can be transferred by a electric current of 1 ampere in 1 second.

3. The drift velocity of electrons is

The drift velocity of the electrons is the order of millimeters per second and the speed of the speed of light is the order of million meters per second, which is approximately 300 million meters per second. That is why the drift velocity of the electrons is very small compared to speed of the light.

4. The charge on an electron is known to be 1.6 × 10-19 coulomb. In a circuit the electric current flowing is 1 A. How many electrons will be flowing through the circuit in a second?

We know that the number of electrons in one coulomb is the ratio of one coulomb to the charge on one electron.

Thus, the number of electrons in a second is equals to 0.625 × 1019

5. In gases the flow of electric current is due to

Basically, the electric current in gases consists of a flow of positive ions in one direction and it together with a flow of negative ion in that opposite direction. Then, the positive charge should have the same magnitude of the negative charge and it must be included as a contribution of the total current. The flow of electric current is referred to the flow of electrons.

6. An electric current of 5 A is same as

The flow of charge per second of time is same as the electric current which flows through the circuit. So, Ampere and Charge / Second are same.

7. An instrument which detects electric current is known as

Voltmeter and Wattmeter cannot be used to measure the electric current and Rheostat would be used to resist the electric current in electrical circuits. The Galvanometer is used to detect the electric current. Because, the galvanometer has a coil that energizes by electric current and according to that current, needle is actuated. Since, it is used to detect some micro ampere electric current only. To measure the high rating currents, it has to be modified as an ammeter.

8. Current flows in a circuit when

While a switch is closed in any circuits, which would make a pathway to flow the electric current into the circuit.

9. Eight-tenths coulomb passes a point in 4 s. The electric current in amperes is

The given terms are, Q = 8/10 C & T = 4 s
We know that, I = Q / t = ( 8 / 10) /4 = 2 / 10 = 0.2
Current, I = 0.2 Amps

10. An ammeter is an electrical instrument used to measure

Ammeter is a tool that is designed to measure the flow of electric current in a circuit.

11. The rate of flow an electric charge is known as

The rate of flow of an electric charge is referred as the movement of electric charges in Coulombs per second of time. This Coulomb / Sec is another unit of current.

12. The minimum requirement for causing flow of electric current are:

We know that, V = IR ⇒ I = V/R. So, any conductor would have their own resistance, because of its resistivity. While a voltage source is applied in this conductor, according to the above expression a electric current flows through the circuit.

13. Which of the following electric current is considered dangerous to the human body

Refer to the table below,

Current level(milli amperes) Probable Effect on Human Body
1mA Perception level. Slight tingling sensation. Still dangerous under certain conditions.
5mA Slight shock felt, not painful but disturbing. Average individual can let go. However, strong involuntary reactions to shocks in this range may lead to injuries.
10mA - 30mA Painful shock, begin to lose muscular control. Commonly referred to as the freezing electric current or let-go range.
30mA - 99mA Extreme pain, respiratory arrest, severe muscular contractions. Individual cannot let go. Death is possible.
100mA - 2,000mA Ventricular fibrillation (uneven, uncoordinated pumping of the heart.) Muscular contraction and nerve damage begins to occur. Death is likely.
> 2,000mA Cardiac arrest, internal organ damage, and severe burns. Death is probable.

14. The ratio of voltage and electrical electric current in a closed circuit

The ratio of voltage to the electric current is referred as the resistance. If the resistance remains constant in an electrical circuit, then the ratio of voltage to the electric current should be constant at all time. Theoretically, the resistance of any electrical circuit would be constant.

15. Current velocity through the copper conductor is

The velocity of electric current through a conductor is given by;
$V =\frac{I}{n\times A\times Q}$
Where,
V = Velocity of the electric current (m/s)
I = Current (Amps)
n = Number of electrons per cubic meter (8.5 × 1028 per m3 for copper)
A = Cross sectional area of conductor (m2)
Q = Charge on a single electron (Coulombs)
If we use this above expression with some practical values, we would get some fraction of nano or pico meter per second of electric current velocity. Itâ€™s too less. Although the drift velocity of electrons is so less but actually electric current travels at a speed of nearly 3×108 m/sec that is the speed of light.

16. Which of the following statements is true?

Basically, galvanometers are ammeters only. In electrical circuits, ammeters are connected in series. If the resistance is very low, then it could allow more electric current to the load without as much as power loss in that resistance.

17. An electric bulb can be worked from

In electric bulb, an electric current would flow through the filament wire and thereby it can be worked. So, we can use any of the power supply source to glow a bulb, because all the power supply would produce electric current while it is connected with source.

18. Electric electric current passing through the circuit produces

If an electric current passes through the inductor or electromagnet, it would create magnetic effect. If an electric current passes through the furnace, it would create thermal effect and if an electric current passes through the electric bulbs, then it would create luminous effect. Thus, an electrical energy can be converted into any kind of energy very easily.

19. When electric current passes through a metallic conductor, it temperature rises. This is due to

When an electric field is applied through a metallic conductor, due to drift velocity, the electrons can be moved to opposite direction of the field, because of their negative charge. This gives the flow of current. The collisions between conduction electrons and atoms are correspondence to the resistance of the metallic conductor. If the collision between conduction electrons and atoms is high, then the resistance value is also high. Due to the presence of resistance, heat is raised in that conductor.

20. If a parallel circuit is opened in the main line, the current

If the main line of any circuit is opened, then there is no way to flow the current. Thus, the electric current is all connected branches with that parallel circuit would be zero.