Current Electricity

51. Resistance of carbon filament lamp as the applied voltage increases.

1. increases
2. decreases
3. remains same
4. none of the above

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52. Sparking occurs when a load is switched off because the circuit has high

1. resistance
2. inductance
3. capacitance
4. impedance

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53. Switching of a lamp in house produces noise in the radio. This is because switching operation produces

1. arcs across separating contacts
2. mechanical noise of high intensity
3. both mechanical noise and arc between contacts
4. none of the above

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54. Temperature co-efficient of resistance is expressed in terms of

1. ohms/°C
2. mhos/ohm°C
3. ohms/ohm°C
4. mhos/°C

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55. The condition for the validity under Ohm's law is that

1. resistance must be uniform
2. current should be proportional to the size of the resistance
3. resistance must be wire wound type
4. temperature at positive end should be more than the temperature at negative end

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56. The filament of an electric bulb is made of

1. carbon
2. aluminium
3. tungsten
4. nickel

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57. The four bulbs of 40 W each are connected in series swift a battery across them, which of the following statement is true?

1. The current through each bulb in same
2. The voltage across each bulb is not same
3. The power dissipation in each bulb is not same
4. None of the above

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58. The hot resistance of the bulb's filament is higher than its cold resistance because the temperature co-efficient of the filament is

1. zero
2. negative
3. positive
4. about 2 ohms per degree

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59. The insulation on a current carrying conductor is provided

1. to prevent leakage of current
2. to prevent shock
3. both of above factors
4. none of above factors

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60. The minimum charge on an ion is

1. equal to the atomic number of the atom
2. equal to the charge of an electron
3. equal to the charge of the number of electrons in an atom
4. zero

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