Class 10 Science Chapter 11 MCQ

Explanation: Electric power is given by P = Voltage x Current SI unit of voltage = volt SI unit of current = Ampere So, its unit is volt ampere.

In series combination of resistances same current flows through each resistor where as in parallel combination same voltage exist across each resistor. Thus, the two resistors of resistances 2 Ω and 4 Ω are connected in series has same current flowing through it.

Power = 1 Kw, In Watt, P= 1000 W Voltage, V = 220 V Current, I = ? Current is given by I = P/V I= 1000/220 I = 4.5 A So, A fuse wire of rating slightly greater than 4.5A must be used i.e. 5A.

Here, all these statements are correct. Hence, your answer will be option [D].

Given resistors, R1 = 2 Ω and R2 = 4 Ω Voltage, V = 6 V1 Time, t = 5 s Resistance, R = 4 Ω Heat dissipated, H = ? Resistor, Rs = R1 + R2 = 2 + 4 = 6 Ω Current, I = V/R = 6/6 = 1A. Heat dissipated H = I¬^2 Rt = 1 x 4x 5 = 20 J

Current is measured by an instrument called ammeter. The ammeter is always connected in series with the circuit in which the current is to be measured.

Resistivity depends on the nature of the material and the temperature but does not depend on the shape of the resistor.

Power is given by, P = I²R P1 = I²R And, P2 = (2I)², R = 4I²R, When current is increased by 100% [It means that current becomes doubled i.e. 2I] Therefore, Increase in power dissipated = P2 – P1 = 4I²R – I²R Change in dissipated power = 3I^2R Increase in percent of power dissipated = 3P1/P1 ×100 = 300%

In first case, Resistivity of the conductor, ƿ = RA¹/ l In second case, Resistivity of the conductor, ƿ = RA¹/ 2l Therefore, for same material, resistivity of the conductor will be same. So, on substituting the value of ƿ in Eq. (ii), we have RA/I = RA¹/2I = A¹ =2A

The current is directly proportional to the potential difference applied across the ends of a conductor it means that if the potential difference across the ends of a conductor is doubled, the current flowing through it also gets doubled, and if the potential difference is halved the current also gets halved.

Here, all these statements are correct. Hence, your answer will be option [D].

The maximum resistance is obtained when resistors are connected in parallel combination. This equivalent resistance will be: Rs = n x R = 5 X 1/5 = 1Ω Rs = equivalent resistance for series combination.

Given, Current, I = 1 A Time, t = 16 seconds No. of electrons, N = ? We know that, Current, I = Q/t = ne/t [e = charge of an electron = 1.6x 10 to the power -19 C and Q = ne] N= It/e = 1 x 16/ 1.6 x 10 to the power -19 = 10 to the power 20

We know that a thick wire has a greater area of cross section; whereas a thin wire has a smaller area of cross section. This means that a thick wire has less resistance and a thin wire has more resistance.

Electrical resistivity of a given metallic wire depends on number density of free electrons in the conductor which is the nature of material. It also depends on the temperature of conductor.

We know that, H = I²Rt It shows that the heat produced is proportional to the square of the current.

Nichrome does not undergo oxidation or burn easily even at high temperature. Due to this nichrome wire can be kept red hot without burning or breaking in air.

It is the temperature of an electric bulb filament when it glows.

The power in watts is found by multiplying the potential difference in volts by the current in amperes. We can write down the above formula for electric power in words as: Electric power = Potential difference x Current

Kilowatt-hour is the commercial unit of electrical energy.

1 kilowatt hour is equal to 3.6 X 10 to the power 6, joules of electrical energy. One kilowatt hour is the amount of energy consumed at the rate of 1 kilowatt for 1 hour. 1 kilowatt hour = 36,00,000 joules (or 3.6 X 10 to the power 6).

A power rating of 100 W on the bulb means that it will consume electrical energy at the rate of 100 joules per second. If we know the power P and voltage V of an electrical appliance, then we can very easily find out the current I drawn by it. This can be done by using the formula: P = V x I

Electrical energy transferred per second, E = V x I x t = 6 V × 0.5 A × 1s = 3 J/s

This is so because in a parallel circuit, if one device fails, it does not affect the working of the other devices.

Since the charge of an electron is 1.6×10−19C, 6.25 × 10 to the power 18 electrons taken together constitute (6.25 × 10 to the power 18 × 1.6 × 10−19 C) or 1 coulomb of charge.