The number of dry cells, each of e.m.f. 1.5 volt and internal resistance 0.5 ohm that must be joined in series with a resistance of 20 ohms, so as to send a current of 0.6 amperes through the circuit is 

(1) 2

(2) 8

(3) 10

(4) 12

For driving a current of 2 A for 6 minutes in a circuit, 1000 J of work is to be done. The e.m.f. of the source in the circuit is 

(1) 1.38 V

(2) 1.68 V

(3) 2.04 V

(4) 3.10 V

Two batteries of e.m.f. 4V and 8 V with internal resistances 1 Ω and 2 Ω are connected in a circuit with a resistance of 9 Ω as shown in figure. The current and potential difference between the points P and Q are 

(1) $\frac{1}{3}A\text{\hspace{0.17em}\hspace{0.17em}and \hspace{0.17em}}3V$

(2) $\frac{1}{6}A\text{\hspace{0.17em}\hspace{0.17em}and\hspace{0.17em} }4V$

(3) $\frac{1}{9}A\text{\hspace{0.17em}\hspace{0.17em}and\hspace{0.17em} 9}V$

(4) $\frac{1}{2}A\text{\hspace{0.17em}\hspace{0.17em}and\hspace{0.17em}\hspace{0.17em}}12V$

Four identical cells each having an electromotive force (e.m.f.) of 12V, are connected in parallel. The resultant electromotive force (e.m.f.) of the combination is :

(1) 48 V

(2) 12 V

(3) 4 V

(4) 3 V

The internal resistance of a cell of e.m.f. 12V is $5\times {10}^{-2}\Omega$. It is connected across an unknown resistance. The voltage across the cell, when a current of 60 A is drawn from it, is :

(1) 15 V

(2) 12 V

(3) 9 V

(4) 6 V

The current in the given circuit is 

(1) 0.1 A

(2) 0.2 A

(3) 0.3 A

(4) 0.4 A

Consider four circuits shown in the figure below. In which circuit power dissipated is greatest (Neglect the internal resistance of the power supply)

(1)

(2)

(3)

(4)

In the circuit, the reading of the ammeter is (assume internal resistance of the battery be zero) :

1. $\frac{40}{29}A$

2. $\frac{10}{9}A$

3. $\frac{5}{3}A$

4. 2 A

Eels are able to generate current with biological cells called electroplaques. The electroplaques in an eel are arranged in 100 rows, each row stretching horizontally along the body of the fish containing 5000 electroplaques. The arrangement is suggestively shown below. Each electroplaques has an emf of 0.15 V and internal resistance of 0.25 Ω 

The water surrounding the eel completes a circuit between the head and its tail. If the water surrounding it has a resistance of 500 Ω, the current an eel can produce in water is about

(1) 1.5 A

(2) 3.0 A

(3) 15 A

(4) 30 A

A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 hours. The mean terminal voltage during discharge is 14 V. The "Watt-hour" efficiency of the battery is :

(1) 82.5%

(2) 80 %

(3) 90%

(4) 87.5%