TOPIC: CURRENT ELECTRICITY
DIRECTION: Choose the correct answer from the lettered options.
1. Which of the following is an electrolyte?
A. Sugar solution
B. Alcohol
C. Paraffin
D. Grape juice
The correct answer is option [D].
2. An equipment whose power is 1500W and resistance 375 Ohms would draw a current of _______.
A. 0.01A
B. 2.00A
C. 4.00A
D. 77.50A
The correct option is [B]
3. A voltmeter has a resistance of 4500Ω and is calibrated to read 2V per division. If the instrument is required to read 10V per scale division; what series resistance must be connected to it?
A. 18,000Ω.
B. 19,000Ω.
C. 20,000Ω.
D. 18,500Ω.
The correct answer is option [A]. Hint: 10V = P.d. across R + P.d. across galvanometer. 10 = 2/4500[R + 4500] → R = 18,000Ω.
4. In the diagram drawn, the ratio of the electric power dissipated in the 6Ω and 3Ω resistors repectively is ______.
A. 1:2
B. 1:3
C. 2:1
D. 2:3
The correct answer is option [A]. P = V2/R The ratio power dissipated in the 6Ω and 3Ω resistors respectively are (12)2/6 : (12)2/3 144/6 : 144/3 24 : 48 1 : 2
5. A wire of length 15m made of a material of resistivity 1.8×10–6Ωm has a resistance of 0.27W. Determine the area of the wire.
A. 1.5 × 10-4m2
B. 1.0 × 10-4m2
C. 2.7 × 10-5m2
D. 7.3 × 10-6m2
The correct answer is option [B]. The resistance of a wire is related of the resistivity r, the length l, and the area cross section by the formula R = rl/A. Given r = 1.8 × 10-6, l = 15m, R = 0.27W, A = ? A = rl/R = (1.8 × 10-6 × 15)/0.27 = 1.0 × 10-4m2
6. Which of the following is an essential property of the wire used for making fuses?
A. High thermal conductivity
B. Low melting point
C. Low electrical resistivity
D. Thick diameter
The correct answer is option [A].
7. The value of a resistivity wire is 1.1 x 10-6Ωcm and the resistance of the wire is 7.029 x 10- 5Ω. Then the length of the wire is ________, if the wire has a diameter of 0.3mm.
A. 65cm
B. 40cm
C. 80cm
D. 64cm
The correct answer is option [D]. Hint: Use the equation R = [ρL]/A, where A = [πD2]/4.
8. The function of the system of granulated carbon mixed with manganese (IV) oxide in a Leclanche′ cell is to _______.
A. increase the e.m.f of the cell to 2.0V
B. prevent local action in the cell
C. prevent polarization in the cell
D. make the cell black and hence a good radiator
The correct answer is option [C].
TOPIC: DENSITY AND RELATIVE DENSITY
DIRECTION: Choose the correct answer from the lettered options.
1. The mass of a stone is 15g when completely immersed in water and 10g when completely in a liquid of relative density 2.0. What is the mass of the stone in air?
A. 25g.
B. 20g.
C. 30g.
D. 35g.
The correct answer is option [B]. Hint: Relative density = 2.0 = [n – 10]/[n – 15], where n = weight of stone in air.
2. If kerosene of density 0.8g/cm3 is mixed with water of 8g, what is the density of the resulting mixture? [Take mass of kerosene = 32g]
A. 0.83g/cm3.
B. 6.25g/cm3.
C. 8.00g/cm3.
D. 0.55g/cm3.
The correct answer is option [A].
3. A heavy bucket of water is lowered down in a well. The upthrust experienced by the bucket of water is _______.
A. U = W + T
B. U = T – W
C. U = W – T
D. W = U – T
The correct answer is option [C]. Note: T = Tension, W = Weight and U = Upthrust.
4. If a solid X floats in liquid P of relative density 2.0 and in liquid Q of relative density 1.5. It can be inferred that _______.
A. weight of P displaced is greater than that of Q
B. weight of P displaced is less than that of Q
C. volume of P displaced is greater than that of Q
D. volume of P displaced is less than that of Q
The correct answer is option [D].
5. If kerosene of density 0.8g/cm3 is mixed with water of 8g, what is the density of the resulting mixture? [Take mass of kerosene = 32g]
A. 0.83g/cm3.
B. 6.25g/cm3
. C. 8.00g/cm3.
D. 0.55g/cm3.
The correct answer is option [A].
6. The mass of a stone is 15g when completely immersed in water and 10g when completely in a liquid of relative density 2.0. What is the mass of the stone in air?
A. 25g.
B. 20g.
C. 30g.
D. 35g.
The correct answer is option [B]. Hint: Relative density = 2.0 = [n – 10]/[n – 15], where n = weight of stone in air.
7. The weight of a solid is measured in air and in a certain liquid of density 0.7g/cm3. If the weight of the solid in air and liquid are 0.09N and 0.02N. Determine the solid’s volume.
A. 20cm3.
B. 15cm3.
C. 10cm3.
D. 5cm3.
The correct answer is option [C]. Hint: Volume, V = [mass of liquid displaced]⁄[density of liquid].
8. A heating coil rated 1000W is used to boil off completely 2kg of boiling water. The time required to boil off the water is ______. [specific latent heat of vaporization of water = 2.3 x 106Jkg-1].
A. 1.15 x 104s
B. 1.15 x 103s
C. 4.6 x 104s
D. 4.6 x 103s
The correct answer is option [D]. IVt = mcθ 1000 x t = 2 x 2.3 x 106Jkg-1 2 x 2.3 x 106/1000 = 4.6 x 103s [Density of water = 1000Kgm-3, g = 10m-2]
9. A cube of sides 0.2m hangs freely from a string. What is the upthrust on the cube when totally immersed in water?
A. 8000N
B. 800N
C. 110N
D. 80N
The correct answer is option [D]. Volume of cube = (0.2)3 = 0.008m3, it will displace water of its own
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