Electrical Engineering- Electric Current and Ohm's Law
Electrical Engineering- Electric Current and Ohm's Law
A standard 60 W bulb is in series with a room heater and connected across the mains. If the 60 W bulb is replaced by 100 W bulb
- the heater output will increase
- ) the heater output will reduce
- the heater output will remains unaltered.
Two aluminium conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional area has a resistance of 100 ohms the resistance of other conductor will be
- 400 ohms
- 100 ohms
- 50 ohms
- 25 ohms.
A nichrome wire used as heater coil has the resistance of 1 ohm/m. For a heater of 1000 W at 200 V, the length of wire required will be
- 10 m
- 20 m
- 40 m
- 80 m.
Variable resistors are
- Wire wound resistors
- Thin film resistors
- Thick film resistors
- All of the above.
Low resistance can be accurately measured by
- Kelvin bridge
- Wheat stone bridge
- Wein's bridge
- None of the above
A heating element of a hot plate on an electric cooking range draws 12 amperes from 240 V mains. How many kWh of energy will be consumed in one hour and 15 minutes
- 1.2
- 3.2
- 6.0
- 7.2.
Temperature coefficient of resistance is expressed in terms of
- ohms / ohms oC
- mhos / ohm oC
- mhos / oC
- ohms / oC.
If R1 is the resistance of a coil of copper at t oC and RT is the resistance at T oC and also the resistance temperature coefficient of copper per degree centrigrade at 0oC is 1/234.45, then Rt/RT
- (1+t) / (1+T)
- (1+ 234.45t) / (1+234.45 T)
- (234.45 + t) / (234.45 + T)
- (234.45 + t2 ) / (234.45 + T 2).
Resistivity is usually expressed in terms of
- mho
- ohm / oC
- ohms/cm-square
- ohms/cm-cube.