CBSE
Multiple Choice QuestionsA voltmeter of resistance 20000 Ω reads 5 volt. To make it read 20 volt, the extra resistance required is
40000 Ω in parallel
60000 Ω in parallel
60000 Ω in series
40000 Ω in series
On increasing the temperature of a conductor, its resistance increases because the
relaxation time increases
electron density decreases
relaxation time decreases
relaxation time remains constant
A circuit consisting of five resistors each of resistance R, forming a Wheatstone bridge. What is the equivalent resistance of the circuit?
2R
R
2R/3
R/2
What is the equivalent resistance between A and B in given figure?
50 Ω
25 Ω
75 Ω
100 Ω
In the given circuit, the voltage across the load is maintained at 12 V. The current in the zener diode varies from 0-50 mA. What is the maximum wattage of the diode?
12 W
6 W
0.6 W
1.2 W
Ten identical cells each of potential E and internal resistance r are connected in series to form a closed circuit. An ideal voltmeter connected across three cells, will read
10 E
3 E
13 E
7 E
Assertion: Long distance transmission of a.c. is carried out at extremely high voltages.
Reason: Because when the distance is large, voltage has to be large.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
A steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor?
Electric field
Drift velocity
Current
Current density
Given that the mobility of electrons in Ge is 0.4 m2 V-1 S-1 and electronic charge is 1.6 × 10-19 C. The number of donor atom ( per m3 ) semiconductor of conductivity 500 mho/m is
8 × 1021
8 × 1015
5 × 1021
8 × 1016
Assertion: Total current entering a circuit is equal to leaving the circuit by Kirchhoff's law.
Reason: It is based on conservation of energy.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
