Relation between Power and Resistance MCQs

Ans. D) 25W

Explanation- Electric power is the rate at which electrical energy is dissipated into the other forms of energy.

Given: Potential difference (V) = 220 V,

Power of the bulb (P)= 110W

Voltage= 110V

Resistance of the bulb is calculated as,

⇒ R = \(\frac{V^2}{P}\) = \(\frac{(220)^2}{100}\) = 484Ω

Power consumed by the bulb is calculated as,

⇒ P = \(\frac{V^2}{R}\) = \(\frac{(110)^2}{484}\) = 25 W

Ans. A) Galvanometer

Explanation- A galvanometer is used to detect current in an electric circuit. It is mainly used in bridges and potentiometers where they indicate the null deflection or zero current.

Ans. B) Series

Explanation- An ammeter is a device which is used to measure the current in a circuit. It is generally connected in series in a circuit. It is because the current remains the same when devices are connected in series.

Ans. B) Siemens

Explanation- The SI unit of conductance = 1/9The SI unit of resistance)= 1/Ω=-1= Siemens.

• Ohm is the SI unit of resistance.
• Ampere is the SI unit of current

Ans. D) 600C

Explanation- It is given that I= 5 A and t= 2 min= 120s

• The total charge on the conductor is given by q = It

⇒ Q = It

⇒ Q = 5 120 = 600C

Ans. D) Aluminium

Explanation- In the given options, Silver has the highest conductivity and aluminium has the least. On a scale of 0 to 100 for electrical conductivity the silver ranks 100 with copper at 97 and gold at 76, aluminium at 60.

Ans. B) Low resistance in parallel

Explanation- A moving coil galvanometer can be converted into an ammeter by connecting a low resistance in parallel to the moving galvanometer.

Ans d) 1127 K

Explanation: Its given that a = 0.00125 per ▫C

R_300K= 1Ω, i.e.

T = 300 – 273 = 27℃

1 = R₀(1 + a x 27) – (1)

Resistance = 2Ω for temperature T.

Hence,

2 = R₀(1 + aT) - (2)

(1) / (2)

(1 + aT) = 2(1 + a x 27)

a(T – 54) = 1

T – 54 = 800

T = 854

T = 854 + 273 = 1127K

Ans. A) Material

Explanation- Since, the resistivity of any conductor is the property of the material. So it is independent of the shape and the size.

It depends on the material of the conductor.

Ans. B) Positive Terminal to Negative Terminal

Explanation- The direction of the conventional current corresponds to the direction of positive charges which is higher potential (positive) to lower potential (negative). 

Electric current is associated with the movement of electrons from lower potential (negative) to higher potential (positive). Therefore, the direction of electric current is opposite to that of conventional current.