A cell of internal resistance \(r\) drives current through an external resistance \(R.\) The power delivered by the cell to the external resistance will be maximum when:
1. \(R=1000 r\)
2. \(R=0.001r\)
3. \(R=2r\)
4. \(R=r\)

In the figure shown, what is the current (in Ampere) drawn from the battery? You are given \(R_1=15~ \Omega, R_2=10~ \Omega, R_3=20~ \Omega,R_4=5~ \Omega, R_5=25~ \Omega, R_6=30~ \Omega, E=15~V\)
  

1. \(7/18\)
2. \(20/3\)
3. \(9/32\)
4. \(13/24\)

The resistive network shown below is connected to a D.C. source of \(16~\text{V}\). The power consumed by the network is \(4\) Watt. The value of \(R\) is:

                          
1. \(16~\Omega\)
2. \(1~\Omega\)
3. \(8~\Omega\)
4. \(6~\Omega\)

A circuit to verify Ohm's law uses ammeter and voltmeter in series or parallel connected correctly to the resistor. In the circuit:

An electric kettle has two heating coils. When one of the coils is connected to an a.c. source, the water in the kettle boils in \(10\) minutes. When the other coil is used the water boils in \(40\) minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be:
1. \(8\) min
2. \(4\) min
3. \(25\) min
4. \(15\) min

The resistance of each arm of the wheat stone bridge is \(10~ \Omega.\) A resistance of \(10~ \Omega\) is connected in series with a galvanometer. The equivalent resistance across the battery will be:
1.\(10~ \Omega\)
2.\(15~ \Omega\)
3. \(20~ \Omega\)
4. \(40~ \Omega\)

In India, electricity is supplied for domestic use at \(220~\text{V}.\) It is supplied at \(110~\text{V}\) in the USA. If the resistance of a \(60~\text{W}\) bulb for use in India is \(R\), the resistance of a \(60~\text{W}\) bulb for use in the USA will be:

Resistances \(n,\) each of \(r~\text{ohm},\)  when connected in parallel give an equivalent resistance of \(R~\text{ohm}.\) If these resistances were connected in series, the combination would have resistance in \(\text{ohms}\) equal to:
1. \(\dfrac{R}{n^2}\)
2. \(\dfrac{R}{n}\)
3. \(nR\)
4. \(n^2R\)

Which of the following \(({I\text-V})\) graphs represents ohmic conductors? 

1.		2.
3.		4.