Explore topic-wise InterviewSolutions in Current Affairs.

Yes, I know the voltage of mains that we use in our household circuits is 120 V.

1. 240 V current disturbs the functioning of organs inside the body. It is called electric shock. If the current flow continues further, it damages the tissues of the body which leads to decrease in resistance of the body. When this current flows for a longer time, damage to the tissues increases and thereby the resistance of human body decreases further. 

2. Hence, the current through the human body will increase. If this current reaches 0.07 A, it effects the functioning of the heart and if this much current passes through the heart for more than one second it could be fatal.

3. If this current flows for a longer time, the person in electric shock will be killed.

The resistance of a conductor increases with the increase of its length.

In a circuit, the battery stores chemical energy, and this energy converts into electric energy.

A potential difference is created between the ends of the conductor, when the battery is connected in a circuit.

Working of a battery : 

• A battery consists of two metal plates (positive electrode = anode and negative electrode = cathode) and a chemical (electrolyte). 
• The electrolyte between the two metal plates consists of positive and negative ions which move in opposite directions.
• The electrolyte exerts a chemical force on these ions and makes them move in a specified direction. 
• Depending upon the nature of the chemical, positive ions move towards one of the plates and accumulate on that plate. 
• As a result of this accumulation of charges on this plate it becomes anode. 
• Negative ions move in a direction opposite to the motion of positive ions and accumulate on the other plate. 
• As a result of this the plate becomes negatively charged called cathode. 
• This accumulation of different charges on respective plates continues till both plates are sufficiently charged. 
• But the ions in motion experience electric force when sufficient number of charges are accumulated on the plates.
• The motion of ions continues towards their respective plates till the chemical force is equal to electric force. 
• Thus the battery works.

Potential Difference: 

Work done by the electric force on unit charge is called potential difference.

V = W/q = Fl/q

Electromotive force (emf): 

The work done by the chemical force to move unit positive charge from negative terminal to positive terminal of the battery.

ε = W/q = Fd/q

Lorentz – Drude theory : 

1. Lorentz – Drude proposed that conductors like metals contain a large number of free electrons. 

2. The positive ions are fixed in their locations. The arrangement of the positive ions is called lattice. 

3. The negative ions (electrons) move randomly in lattice in an open circuit. 

4. When the lattice is closed the electrons are arranged in ordered motion. 

5. When the electrons are in order motion, there will be a net charge (crossing through any cross section. 

6. This order motion of electrons is called electric current.

Correct option is  A) R₁

When the current flows through the body the functioning of organs inside the body gets disturbed. This disturbance inside the body is felt as electric shock.

A) Both statements are true

C) 1 → b, 2 → a, 3 → d, 4 → c

1. electrical energy 

2. less 

3. 6 Ω 

4. volt 

5. Ampere 

6. 12 Ω

7. 11/12 Ω

8. 1 ampere

Correct option is  B) 8 V

Correct option is  C) 0.5 A

The obstruction to the motion of the electrons in a conductor is called resistance of a conductor.

Resistivity is a constant.

In R = pl/A, p is called the resistivity

p = r x A/ l

The materials which can’t conduct electricity are called insulators or non – conductors. 

Eg: Wood, Rubber

In a circuit, the battery stores chemical energy and this energy converts into electric energy. Thus a battery works.

i. When a charge Q flows from the higher potential point to the lower potential point, its potential energy decreases by an amount,

∆U = QV = I∆tV

where I is current due to the charge Q flowing in time ∆t.

ii. By the principle of conservation of energy, this energy is converted into some other form of energy.

iii. In the limit as ∆t → 0, \(\frac{dU}{dt}\) = IV

Here, \(\frac{dU}{dt}\) is power, the rate of transfer of energy ans is given by p = \(\frac{dU}{dt}\) = IV

Hence, power is transferred by the cell to the resistor or any other device in place of the resistor, such as a motor, a rechargeable battery etc.

iv. Due to the presence of an electric field, the free electrons move across a resistor and their kinetic energy increases as they move.

v. When these electrons collide with the ion cores, the energy gained by them is shared among the ion cores. Consequently, vibrations of the ions increase, resulting in heating up of the resistor.

vi. Thus, some amount of energy is dissipated in the form of heat in a resistor.

vii. The energy dissipated per unit time is actually the power dissipated which is given by,

P = \(\frac{V^2}{R}\) = I²R

Hence, it is the power dissipation across a resistor which is responsible for heating it up.

viii. For example, the filament of an electric bulb heats upto incandescence, radiating out heat and light.

1. Electrical device like electric bulb, iron box and regulators are some applications of Ohm’s Law. 

2. Fuse in household circuits is also another application of Ohm’s Law.

(B) copper strip decreases germanium increases. and that of

A) chemical energy converts into electrical energy

Correct option is  C) lattice

B) series to live wire

C) Both Drude & Lorentz

A) Both statements are true

Correct option is  A) 0.1 W

The obstruction offered to the flow of electrons in a conductor is called the resistance

Yes, it varies

(C) 1.0 × 106 + 10%

If potential difference of 1 volt across a conductor produces a current of 1 ampere through it, then the resistance of the conductor is one ohm.

Correct option is: (D) 3 × 10²⁰

Correct option is: (C) Ω m

Correct option is: (C) J/C

1. Reciprocal of resistance is called conductance.

C = \(\frac{I}{R}\)

2. S.I unit statement or Ω^-1

According to Ohm’s law, the potential difference between the ends of a conductor is directly proportional to the electric current passing through it at a constant temperature.

Based on Ohm’s law materials are classified into two categories.

• They are ohmic conductors and non-ohmic conductors.
• Metals obey Ohm’s law. They are called ohmic conductors.
• LEDs are non-ohmic conductors. They don’t obey Ohm’s law.
• Ohm’s law is not applicable to gaseous conductors and semi-conductors

Correct option is  B) Glass

Current density, \(\overset\rightarrow{j}=\frac{1}{ρ}\,\overset\rightarrow{E}\) = σ \(\overset\rightarrow{E}\)

where, ρ = resistivity of the material

E = electric field intensity

σ = conductivity of the material

Correct option is  C) 4 Ω

Correct option is  D) 2

1. The wires which are used for connections and for power transmission are made of material such as copper or aluminium. 

2. The reason is their resistivity is very small and they are made thick so that their resistance can be considered to be negligible. 

3. Further, the loss of electrical energy due to heating is also negligible in them.

1. In an ideal e.m.f. device, there is no internal resistance to the motion of charge carriers.

2. The emf of the device is then equal to the potential difference across the two terminals of the device.

1. In a real emf device, there is an internal resistance to the motion of charge carriers.

2. If such a device is not connected in a circuit, there is no current through it.

1. A switch should not be touched with wet hands. 

2. If water reaches the live wire, it forms a conducting layer between the hand and the live wire of the switch through which the current passes to the hand, and the person may get a total shock

Yes, it does.

1. Lead is used in making fuses because it has low melting point EK resistivity.

2. If the current in the lead wire exceeds certain value, the wire will heat up and melt, so the circuit in the households is opened and all the electric devices are saved.

Alloys are homogeneous mixtures of two or more metals. Generally alloys have more resistivity than the metals from which they have been prepared. As the resistivity increases heating effect of conductor also increases. So alloys are preferred in heating devices.

Electric devices are connected either in series or parallel in circuits