DC basic

 DC basic

1. Ohm's law is applicable to
A ) semiconductor
B ) vacuum tubes
C ) electrolytes
D ) carbon resistor
E ) arc lamps
F ) none of these

2. Resistance of a wire always increases if
A ) temperature is reduced
B ) temperature is increased
C ) number of free electrons available become less
D ) number of free electrons available become more

3. Pure metals generally have
A ) high conductivity and low temperature coefficient
B ) high conductivity and large temperature coefficient
C ) low conductivity and zero temperature coefficient
D ) low conductivity and high temperature coefficient

4. If the length of a wire of resistance R is uniformly stretched to n times its original value , its new resistance is
A ) n R
B ) R / n
C ) n 2 R
D ) R / n2

5. Specific resistance of a conductor depends upon
A ) dimensions of the conductor
B ) composition of conductor materials
C ) resistance of the conductor
D ) both A and B

6. The temperature coefficient of resistance of an insulator is
A ) positive and independent of temperature
B ) negative and independent of temperature
C ) negative and dependent on temperature
D ) positive and dependent on temperature

7. Twelve 1 ohm resistance are used as edges to form a cube .the resistance between two diagonally opposite corner of the cube is
A ) 5/6 ohms
B )1 ohm
C ) 6/5 ohms
D ) 3/2 ohms

8. Which of the following does not use heating effect of electric current ?
A ) Electric furnace
B ) Geyser
C ) Electric iron
D ) vacuum cleaner
E ) electric oven
F ) immersion heater

9. A network consists of linear resistor and ideal voltage source. If the value of the resistor are doubled , then voltage across each resistor
A ) halved
B ) doubled
C ) increased four lines
D ) not changed

10. Two heaters , rated at 1000 W , 250 V each are connected in series across a 250 V , 50 Hz ac mains . The total power drawn from the supply , would be ........W.
A ) 1000
B ) 500
C ) 250
D ) 2000