Q.1
If 2.2 kilo watt power is transmitted through a 10Ω line at 22000 volt, the power loss in the form of heat will be [ MPPMT 1998]
  • a) 0.1 watt
  • b) 1.0 watt
  • c)10 watt
  • d)100 watt
Q.2
If a high power heater is connected to electric mains, then the bulb in the house become dim because [ BHU 1999]
  • a) current drop
  • b) potential drop
  • c) no current drop
  • d) no potential drop
Q.3
Fuse wire should have [ BHU 1999]
  • a)low resistance, high melting point
  • b) low resistance low melting point
  • c)high resistance, low melting point
  • d)high resistance, high melting point
Q.4
An electric kettle has two heating elements. One brings it to boil in 10 minutes and the other in fifteen minutes. If two heating filaments are connected in parallel, the water in kettle will boil is [ KCET 2000]
  • a) 6 minutes
  • b) 8 minutes
  • c)25 minutes
  • d)5 minutes
Q.5
Two 220 volt, 100 watt bulbs are connected first in series and then in parallel. Each time the combination is connected to a 220 volt a.c. supply line. The power drawn by the combination in each case respectively will be [ CBSE 2003]
  • a) 50 watt, 100 watt
  • b) 100 watt, 50 watt
  • c)200 watt, 150 watt
  • d)50 watt, 200 watt
Q.6
A d.c. voltage with appreciable ripple expressed as V=V1 + V2 cos ωt is applied to a resistor R. The amount of heat generated per second is given by [ IAPT 1999]
  • a)
    ch-15_qn-157choice_img_no1.png
  • b)
    ch-15_qn-157choice_img_no2.png
  • c)
    ch-15_qn-157choice_img_no3.png
  • d)None of the above
Q.7
How many lamps each of 50 W and 100 V can be connected in parallel across a 120 V battery of internal resistance 10Ω, so that each flows to full power?
  • a) 2
  • b) 4
  • c)6
  • d)8
Q.8
A heater boils 1 kg water in time t1 and other heater in time t2 if the heaters are connected in series, the combination will boil the same water in times
  • a)
    ch-15_qn-159choice_img_no1.png
  • b)
    ch-15_qn-159choice_img_no2.png
  • c)
    ch-15_qn-159choice_img_no3.png
  • d)
    ch-15_qn-159choice_img_no4.png
Q.9
Fifty electric bulbs are connected in series across a 220 V supply and the illumination produced is I1 . Five bulbs are fused and remaining forty five bulbs are connected in series, the illumination produced is I2, by what percentage illumination will change
  • a) increase by 10%,
  • b) decrease by 11%,
  • c) increase by 11%,
  • d) decrease by 11%,
Q.10
A uniform wire connected across a supply produces heat H per second. If the wire is cut into three equal parts and all the parts are connected in parallel across the same supply, the heat produced per second will be
  • a) H/9
  • b) 9H
  • c)3H
  • d)H/3
Q.11
Find heat produced per minute in the resistance R2 shown in circuit
ch-15_que_no-162_img_no1.png
  • a) 640 J
  • b) 1280 J
  • c)960 J
  • d)320 J
Q.12
Masses of three wires are in the ratio of 1:3:Their lengths are in ratio of 5:3:When connected in series with battery the ratio of heat produced in them will be
  • a) 1:3:5
  • b) 5:3:1
  • c)1:15:125
  • d)125:15:1
Q.13
An electric heating element consumes 500W when connected to a 100V line. If the line voltage becomes 150V, the power consumed will be [ Roorkee 1990]
  • a) 500W
  • b) 750 W
  • c) 1000 W
  • d) 1125 W
Q.14
A fuse wire with circular cross-sectional radius of 0.02 mm blows with a current of 5 amp. For what current, another fuse wire made from the same material with cross sectional radius of 0.4mm will blow
  • a)14.7 A
  • b) 5 A
  • c)3 A
  • d)1.5 A
Q.15
The charge Q flowing through a resistance R varies with time t as Q=at - btThe total heat produced in R is
  • a) a3R / 6b
  • b) a3R / 3b
  • c)a3R / 2b
  • d)a3R / b
Q.16
A 100 W bulb B1 and 60W bulb B2 and B3 are connected to a 250 V source as shown in figure . Now W1, W2, W3 are the output power of the bulb B1, B2 and B3 respectively. Then
  • b) W1 > W2 > W3
  • d)W1 < W2 < W3
  • a) W₁ > W₂=W₃
  • c)W₁ < W₂=W₃
Q.17
An electric kettle taking 3A at 200V brings one litre of water from 20°C to the boiling point in 10 minutes. Its efficiency is
  • a) 33.3%
  • b) 66.6%
  • c) 87.7%
  • d) 93.3%
Q.18
Time taken by 836W water to heat one litre of water from 0°C to 40°C is
  • a)50 sec
  • b) 100 sec
  • c)150 sec
  • d)200 sec
Q.19
The same mass of copper is drawn into two wires of thickness 1mm and 2mm. If two wires are connected in series and current is passed, then heat produced in the wire is in the ratio of
  • a) 16:1
  • b) 9:4
  • c)1:16
  • d)4:9
Q.20
The water in an electric kettle begins to boil in 15 minutes after being switched on. Using the same mains supply, should the length of the wire used as heating element, be increased or decreased if the water is to boil in 10 minutes
  • a) increased by 10%
  • b) decreased
  • c) increased by 50%
  • d) unchanged
Q.21
A 100 W immersion heater is placed in pot containing 1 litre of water at 20°C. How long it will take to heat the water to boiling temperature, if 20% of the available energy is lost to surroundings?
  • a)18 minutes
  • b) 16 minutes
  • c)14 minutes
  • d)20 minutes
Q.22
Two electric bulbs A and B are designed for the same voltage. Their power ratings are PA and PB respectively, with PB > PA. If they are joined in series across a V volt supply
  • a) B will draw more power than A
  • b) A will draw more power than B
  • c)the ratio of powers drawn by them will depend on V
  • d)A and B will draw the same power
Q.23
Ratio of the amount of heat developed in the four arms of a balanced wheat stone bridge, when the arms have resistance P=100Ω, Q=10Ω, R=300 Ω and S=30 Ω respectively is
  • a) 3:30:1:10
  • b) 30:3:10:1
  • c)30:10:1:3
  • d)30:1:3:10
Q.24
Twenty one similar electric bulbs, each of resistance r are connected in series across 220 V supply. After one bulb is fused, the remaining bulbs are connected again in series cross the same supply. The percentage total change in illumination of bulbs is
  • a) decrease by 5%
  • b) increase by 5%
  • c) decrease by 10%
  • d) increase by 10%
Q.25
The current capacity of a storage cell is 3 Ah. The maximum current it can supply for half hour is
  • a)1.5 A
  • b) 3 A
  • c)4.5 A
  • d)6.0 A
Q.26
The current capacity of the charged secondary cell does not depend on
  • a) rate of discharge
  • b) temperature
  • c)amount of active material
  • d)rate of charging
Q.27
The amount of ions liberated by 96500C charge passed through the electrolyte is called
  • a) electrochemical equivalent
  • b) chemical equivalent
  • c)gram equivalent
  • d)none of the above
Q.28
Which of the following acts as depolariser in Leclanche cell?
  • a) MnO2
  • b) NH4Cl
  • c) Mn2O3
  • d) ZnCl2
Q.29
The power of heater is 750W at 1000°C. What will be its power at 200°C if α=4 ×10⁻⁴C
  • a) 500 W
  • b) 990 W
  • c)250 W
  • d)1500 W
Q.30
The power of heater is 500 W at 800° C. What will be its power t 200°C if α=4 ×10⁻⁴ per °C?
  • a)484 W
  • b) 672 W
  • c)526 W
  • d)611 W
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