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(i) – (e) 

(ii) – (d) 

(iii) – (a) 

(iv) – (b)

(i) – (c) 

(ii) – (d) 

(iii) – (b) 

(iv) – (a)

(d) Assertion is true and Reason explains Assertion

Correct answer is (a) 5 A

(i) – (d) 

(ii) – (c) 

(iii) – (a) 

(iv) – (b)

(i) – (e) 

(ii) – (a) 

(iii) – (d) 

(iv) – (c)

(b) electric power

Correct answer is (b) 746 W

In an electrical circuit the current flows from the positive to the negative. The conventional current always flows in the direction opposite to the direction of flow of the electron.

If a body has positive charge it means that it has less no. of electrons than the no. of protons. Due to this imbalance of the charges, the body will attract the negative charged body

Incandescent, fluorescent, CFL, LED bulbs etc. are different types of bulbs.

(a) For identical bulbs in series- same current, same potential difference. 

(b) For identical bulbs in parallel- same potential difference, different current. 

(c) For unidentical bulbs in series- same current, different potential difference. 

(d) For unidentical bulbs in parallel- different current, same potential difference.

(i) The resistance of a semi conductor decreases with increase in temperature. 

(ii) The resistance of an alloy remains nearly unaffected by the change in temperatue.

When a given metallic wire is doubled on itself, its length is reduced to half, but its area of cross section gets doubled. So, the resistance of the wire will become one-fourth i.e., the new resistance of wire will be R/4 (or 0.25R). 

Given: 

Resistance R = 3Ω 

Original length L₁ = 15cm = 0.15m 

New length, L₂ = 45 cm = 0.45 m 

Formula Used: 

Resistance, R = \(\frac{ρL}{A}\)

Where, 

ρ is resistivity of the wire 

L is the length of the wire 

A is the area of the wire. 

Now, \(\frac{R_1}{R_2}=\frac{ρL_1\,\times\,A}{A\,\timesρL_2}\)

⇒ \(\frac{3\,Ω}{R_2}=\frac{0.15m}{0.45m}\)

⇒ R₂ = \(\frac{3Ω\,\times\,0.45\,m}{0.15\,m}\)

= R₂ = 9 Ω 

Hence, the new resistance is 9 Ω

R’ = n²R 

= 2² × 6 = 24 Ohm.

Resistivity remains unchanged because resistivity depends on the nature of material not on Length.

When a given wire is stretched to double its length, its area of cross-section will be halved, so the resistance of wire will become four times.

(i) The resistance of a wire increases with increases in the length of wire (R ∝ l). 

(ii) The resistance of a wire decreases with increase in its thickness (R ∝ l/a where a = πr², the area of crosssection of the wire). 

(iii) The resistance of a metallic wire increases with increase in its temperature.

The S.I. unit of electrical resistance is ohm (Ω). The resistance of a conductor is said to be 1 ohm if 1 ampere current flows through it when the potential difference across its end is 1 volt.

By reducing the length of element the resistance will decrease. Power is inversely proportional to resistance. So, this will result in more consumption of energy.

True 

In parallel connection the voltage across the resistance is the same.

DISTINCTIONS BETWEEN CONDUCTORS AND INSULATORS OF ELECTRICITY:

The heating elements of electric toasters and electric irons are made of an alloy rather than a pure metal due to the following reasons : 

(i) Alloys do not oxidise readily at high temperature.

(ii) Alloys have higher resistivity than their constituent elements.

(i) Length of conductor. (ii) Area of cross-section of conductor. (iii) Material of conductor. (iv) Temperature of conductor.

The resistivity of an alloy is generally higher than that of its constituent metals. Alloys do nor oxidise (burn) readily at higher temperatures. Therefore, conductors of electric heating devices, such as toasters and electric irons, are made of an alloy rather than pure metal.

The e.m.f. of different cell depends on the following factors: 

(i) The material of the electrodes. 

(ii) The electrolyte used in the cell. It is to be noted that the e.m.f. of a cell does not depend on its shape or size.

Given P = 12W, V = 12V,t = 60 sec P = VI

I = P/V = 12/12 = 1A

V = IR

R = V/I = 12/1 = 12 ohm

H = I²Rt

H = I² x 12 x 60

H = 720 J

Correct option is C) 1000

Current remains constant.

The resistivity of an alloy is generally higher than that of its constituent metals. Alloys do not oxidise (burn) readily at high temperatures. Because of this reason the conductors of electric heating devices, such as bread-toasters and electric irons made of an alloy rather than a pure metal.

Conductors 

1. Conductors are those subs¬tances which allow electricity to flow through them. 

2. e.g. all metals, human body. 

Insulators 

Insulators are those which do not allow electricity to pass through them. 

– e.g. wood, paper, glass.

If we use a group of two or more cells, it is called a battery. A battery is used where we require more electricity.

The factors which govern the internal resistance of cell are: 

(i) The surface area of the electrodes: The larger the surface area, less is the internal resistance. 

(ii) The distance between the electrodes: As the distance between the electrodes increases, the internal resistance of cell also increases. It is also affected by the nature, concentration and temperature of the solution (electrolyte). 

Nichrome, due to its high resistivity.

C) Miniature circut breaker

An ammeter used for measuring an electric current flowing in an electric circuit.

We use series connection of bulbs for decoration purpose, parallel connection of bulbs in house hold connections.

Electric lamps are connected in parallel. 

Electrical power in terms of current and resistance is P = I²R.