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Why are we looking at alternate sources of energy?

We are looking for alternative sources of energy because fossil fuels are non-renewable sources of energy. They are not available in large... View Article

Why copper and aluminium wires are usually employed for electricity transmission?

Copper and aluminium are good conductors of electricity also they have low resistivity. So they are usually used for electricity transmission.... View Article

How does the resistance of a wire vary with its area of cross-section?

Electrical resistance is directly proportional to the length (L) of the conductor and inversely proportional to the cross-sectional area (A). It... View Article

Why is the series arrangement not used for domestic circuits?

In series circuits voltage is divided. Each component of a series circuit receives a small voltage so the amount of current decreases and the... View Article

Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?

Materials that permit electricity or heat to pass through it is called conductors. Alloys are combinations of metals or metals and other... View Article

Why is the tungsten used almost exclusively for filament of electric lamps?

Tungsten is used as filament in electric bulbs The melting point and resistivity of Tungsten are very high. At high temperatures, it does... View Article

Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?

The energy consumed by electrical appliances is given by the equation Electric power is the rate of consumption of electrical energy by electric... View Article

A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R′, then the ratio R/R′ is _____. (a) 1/25 (b) 1/5 (c) 5 (d) 25

Given that The resistance is cut into five equal parts Find out The equivalent resistance of this combination is R′, then the ratio... View Article

Define the unit of current.

The unit of current is Ampere. Ampere is denoted as A. The SI unit of current is an ampere that measures the flow of electric charge... View Article

The following real numbers have decimal expansions as given below. In each case, decide whether they are rational or not. If they are rational, and of the form, p q what can you say about the prime factors of q? (i) 43.123456789 (ii) 0.120120012000120000.

A rational and irrational number. The rational numbers are the numbers that can be represented in p/q form where q is not equal to zero. It is... View Article

Without actually performing the long division, state whether the following rational numbers will have a terminating decimal expansion or a non-terminating repeating decimal expansion: (i) 13/3125 (ii) 17/8 (iii) 64/455 (iv) 15/1600 (v) 29/343 (vi) 23/(2352) (vii) 129/(225775) (viii) 6/15 (ix) 35/50 (x) 77/210

Solutions: To state whether the following rational numbers will have a terminating decimal expansion or a non-terminating repeating decimal... View Article

Prove that the following are irrationals: (i) 1/√2 (ii) 7√5 (iii) 6 + √2

Solution: Let us assume 1/√2 is a rational number Let us assume 1/√2 = r where r is a rational number On further calculation we... View Article

There is a circular path around a sports field. Sonia takes 18 minutes to drive one round of the field, while Ravi takes 12 minutes for the same. Suppose they both start at the same point and at the same time, and go in the same direction. After how many minutes will they meet again at the starting point?

Given that Sonia takes 18 minutes to drive one round of the field, while Ravi takes 12 minutes for the same. Find out After how many minutes will... View Article

Check whether 6ⁿ can end with the digit 0 for any natural number n.

Given A number 6n Find out We need to check whether it can end with zero Solution We know that any number is multiplied by 5 or 10 or by the... View Article

Find the LCM and HCF of the following pairs of integers and verify that LCM × HCF = product of the two numbers. (i) 26 and 91 (ii) 510 and 92 (iii) 336 and 54

Answer: In arithmetic, the least common multiple or LCM of two numbers say a and b, is denoted as LCM (a,b). The LCM is the smallest or least... View Article

Express each number as a product of its prime factors: (i) 140 (ii) 156 (iii) 3825 (iv) 5005 (v) 7429

On taking the LCM of 140, we will get the product of its prime factor. Therefore, 140 = 2 × 2 × 5 × 7 × 1 =... View Article

An army contingent of 616 members is to march behind an army band of 32 members in a parade. The two groups are to march in the same number of columns. What is the maximum number of columns in which they can march?

Given An army contingent of 616 members is to march behind an army band of 32 members in a parade. Find out The maximum number of columns in... View Article

Give examples to show that friction is both a friend and a foe.

(i) Friction allows us to grip and catch different objects. (ii) It helps us to walk comfortably on the surface. (iii) It helps to minimize the... View Article

Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?

The force of friction between the two surfaces will increase if the two surfaces are pressed harder against each other. Thus, larger force will... View Article

Explain why sportsmen use shoes with spikes.

Spikes increase the surface of the shoes & make it rough which results in an increase in friction. This helps to have more grip on the floor... View Article