The length of a potentiometer wire is 5 metres. An electron in this wire experiences a force of 4.8 × 10-19 newton, emf of the main cell used in potentiometer is
infinite
zero
minimum
maximum
n equal resistors are first connected in series and then connected in parallel. What is the ratio of the maximum to the minimum resistance ?
n
1/n2
n2
1/n
A storage battery is connected to the mains for charging with emf of 12.5 V. The internal resistance of the storage battery is 1 Ω. When the charging current is 0.5 A, the potential difference across the storage battery is
13 V
12.5 V
12 V
11.5 V
The resistor R1 dissipates power P, when connected to a generator. If a resistor R2 is inserted in series with R1, the power dissipated by R1
increases
decrease
remains the same
may increase or decrease depending on the value fo R1 and R2
Potentiometer measures the potential difference more accurately than a voltmeter because
it has a wire of high resistance
it has a wire of low resistance
it does not draw current from external circuit
it draws a heavy current from external circuit
A condenser having a capacity of 2 μF is charged to 200 V and then the plates of the capacitor are connected to a resistance wire.The heat produced is
2 x 10-2 J
4 x 10-2 J
4 x 10-4 J
4 x 1010 J
In a potentiometer of 10 wires,the balance point is obtained on the 7th wire.To shift the balance point to 9th wire,we should
decrease resistance in the main circuit
increase resistance in the main circuit
decrease resistance in series with the cell whose emf is to be measured
increase resistance in series with the cell whose emf is to be determined
The resistance of a discharge tube is
ohmic
non - ohmic
infinity
A 2 kW boiler used for 1 hour everyday consumes electrical energy in thirty days equal to
120 units
60 units
15 units
30 units
The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use?
20 Ω
40 Ω
200Ω
400Ω
