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What would be the danger involved in replacing a blown fuse with the one which would carry a large current?
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An electric kettle has a heating element which is rated at 2 kW when connected to a 250 V electric supply. Calculate the
(a) Current which flows in the element when it is connected to a 250 V supply,
(b) Resistance of the filament,
(c) Heat produced in 1 minute by the element,
(d) Cost of running the kettle for 10 minutes a day for 30 days of the month, at the rate of Rs. 3.00 per unit.
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60 joules of heat was dissipated in a resistor when 20 C flowed for 5 s. Calculate:
(a) P.d. across the resistor,
(b) Resistance of the resistor, and
(c) Average power dissipated in the resistor.
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Fig. shows a 3 pin plug with the cover removed. The electric cable
connected to the plug contains 3 wires with colour coded insulation namely brown, blue and green.
- Identify each of the colour coded wires by stating to which of the
terminals A, B or C in the diagram they should be connected. - Identify the terminal through which no current passes in normal
circumstances. - What is the purpose of the earthed wire connected to an electric
appliance like an electric heater? Describe how it works.
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In a house there are 6 bulbs of 100 W each used for 4 hours a day, 4 bulbs of 60 W each used for 8 hours a day, an immersion heater of 2.5 kW used for 1 hour per day, and an electric iron of 800 W used for 2 hours per day. Calculate the cost of monthly electric bill for the month of April at the rate of 80 p per unit.
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An electric oven is rated as 1.5 kW, 250 V. If it is connected to a 250 V mains, calculate the
(a) Current drawn,
(b) Energy consumed in 20 hours,
(c) Cost of energy consumed in 20 hours at the rate of Re. 1 per unit.
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An auto lamp is joined to a battery of e.m.f. 4 V and internal resistance 2.5Ω. A steady current of 0.5 A flows through the circuit. Calculate the
(a) Total energy provided by battery in 10 minutes,
(b) Heat dissipated in the bulb in 10 minutes.
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Explain with the help of a diagram how does 'short circuiting' occur in an electric kettle.
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Electrical appliances have voltage and power ratings as listed below. Which
has the larger working resistance?
| Appliances | Voltage (V) | Power (W) |
| (a) Washing machine | 250 | 3000 |
| ( b) Television | 240 | 160 |
| (c)240 | 240 | 1500 |
| ( d) Hair curler | 250 | 20 |
| ( e) Car head lamp | 12 | 36 |
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If the potential differences between two parts of a thundercloud is 10s V,
what is the amount of energy given up during the passage of 20 coulombs?
(a)2x10-7J
(b)200J
(c)Sx106 j
(d)2x 109J
(e)2x 1010 J
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A 3 pin mains plug is fitted to the lead for a 1 kW electric kettle to be used on a 250 V A.C. supply. Which of the following statements is NOT correct?
(a) A 13 A fuse is the most appropriate value to use.
(b) The brown wire should be connected to the live side of the mains.
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Name the principle on which a transformer works.
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What is the function of a step-up transformer?
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A wire is passed through a piece of cardboard as shown in fig .. An electric current flows vertically down the wire and then flows back up. The two sections of the write are observed to repel each other.
(a) Wi th the aid of a diagram, describe how you would plot the magnetic field lines on the card .
(b) Sketch the magnetic field patterns around both the sections of the wire. Use your sketch to explain why the two sections repel each other.
(c) The repulsive force between the two sections is small. What changes could be made to increase it?
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The circuit diagram in fig shows two coils of an insulated copper wire wound on a cardboard tube. G is a center zero galvanometer.
(a) Describe what will happen when th e swi tch K is cl osed for severa l
seconds and then opened again .
(b) What will be the effect of repeating the experiment with an iron placed in the tube?
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