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
A steady current of 1.5 A flows through a copper voltameter for 10 min. If the electrochemical equivalent of copper is 30 ×10-5g C-1,the mass of copper deposited on the electrode will be :
0.40 g
0.50 g
0.67 g
0.27 g
The negative Zn pole of a Daniell cell, sending a contant current through a circuit, decreases in mass by 0.13 g in 30 minutes. If the electrochemical equivalent of Zn and Cu are 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is
0.180 g
0.141 g
0.126 g
0.242 g
An electirc kettle boils 1 kg of water in time t1 and another kettle boils the same amount of water in time t2. When they are joined in series, the time required to boil 1 kg of water is
t1 + t2
Two identical batteries each of emf 2 V and internal resistance 1Ω are available to produce heat in an external resistance by passing a current through it. The maximum power that can be developed across R using these batteries is
3.2 w
2.0 w
1.28 w
W
In india electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be
R
2R
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
200 Ω
400 Ω
In electrolysis the mass deposited on an electrode is directly proportional to :
current
Square of current
concentration of solution
Inverse of current
A 10 metre potentionmeter wire has a resistance of 20 Ω. It is connected in series with a battery of emf 2.5 volt and a resistance of 5 Ω. The potential gradient along wire in volt cm-1 is
0.002
0.02
0.2
0.0025
Kirchhoff's current law at a junction deals with conservation of
charge
energy
momentum
all of these