Two batteries of emf 4V and 8V with internal resistance are connected in a circuit with a resistance of as shown in figure. The current and potential difference between the point P and Q are
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
The resistance of a discharge tube is
zero
ohmic
non - ohmic
infinity
A battery is charged at a potential of 15V for 8 h when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 h. The mean terminal voltage during discharge is 14 V. The "watt-hour" efficiency of the battery is
82.5%
80%
90%
87.5%
A piece of copper and another of germanium are cooled from room temperature to 80K.The resistance of
each of them increases
each of them decreases
copper increases and germanium decreases
copper decreases and germanium increases
