In the network shown, the equivalent resistance between A and B is 4 3 Ω , find the value of r .

The equivalent circuits are shown. While making equivalent circuits we have to take care that each resistor should be attached to same potential difference that is why 3Ω and r resistors can be shown as separate as their ends are at potential of P and Q. 1 R = 1 3 + 1 4 + 1 r ⇒ 1 r = 3 4 - 1 3 - 1 4 ⇒ 1 r = 2 12 ⇒ r = 6 Ω

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While charging a run-down battery, current flows inside it from its negative terminal to positive terminal.

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Important Questions on Current Electricity

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Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Two cells of internal resistances

r_{1}

and

r_{2}

and of the same emf are connected in series, across a resistor of resistance

R

. If the terminal potential difference across the cells of internal resistance

r_{1}

is zero, then the value of

R

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

A cell of

e . m . f . 10 V

and internal resistance

3 Ω

is connected to a resistor in series. If the current in the circuit is

0.5 A

, then find out the resistance of the resistor and terminal voltage across the cell.

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

E.M.F. of an electrical cell is

2 V

. A

10 Ω

resistance is joined at its two ends then the potential difference is measured

1.6 V

. Find the internal resistance and lost volt.

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

There are only

2 Ω

carbon resistors in stock. A circuit needs

3 Ω

resistance. How will you connect the resistors to get the required resistance using minimum numbers?

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Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Write the relation of e.m.f of a cell and its internal resistance. What is the condition under which the potential difference between the terminals of the cell and its e.m.f are equal?

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Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

In the network shown, the equivalent resistance between $A$ and $B$ is $\frac{4}{3} Ω$ , find the value of $r$ .

Question Image

HARD

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Obtain the expression for the effective emf and the effective internal resistance of two cells connected in parallel such that the currents are flowing in the same direction.

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Establish the relationship between electromotive force, terminal voltage and internal resistance.

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Derive the expression for equivalent emf (

E_{eq}

) for the cells in series combination.

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

A resistor is connected across a cell of

emf 1.5 V

having an internal resistance of

1 Ω

. If a current of

200 mA

flows through the resistor, find the potential difference between the electrodes of the cell.

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Two cells of

emf 6 V

and

3 V

of internal resistances

1 Ω

and

2 Ω

respectively are connected in parallel with their positive terminals together and similarly the negative terminals together. The equivalent

emf

of the combination would be

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Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Two cells of the same EMF $E$ but different internal resistances $r_{1}$ and $r_{2}$ are connected in series with an external resistance $R$ as shown in the figure. The terminal potential difference across, the second cell is found to be zero. The external resistance $R$ must then be:

Question Image

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Define internal resistance of a cell. State two factors on which it depends.

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Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

A cell of emf

4 V

and internal resistance

0.2 Ω

is connected with the resistance of

1.8 Ω

. The voltage across the cell terminal will be

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Explain with circuit diagram the parallel combination of identical cells. Obtain the condition for maximum current in the external resistance connected with the combination.

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Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

Two cells of emf

E_{1}

and

E_{2}

having internal resistances

r_{1}

and

r_{2}

respectively are connected in parallel. Deduce the expression for the equivalent

emf

and equivalent internal resistance of this parallel combination.

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

The storage battery of a car has an emf of

12 V

. If the internal resistance of the battery is

0.4 Ω

, what is the maximum current that can be drawn from the battery?

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

A battery of

e . m . f .

5 V

and internal resistance

2.0 Ω

is connected to an external resistance. If the current in the circuit is

0.4 A

, the terminal voltage of the battery is

EASY

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

A battery of e.m.f $12 V$ and internal resistance $0.5 Ω$ is charged by a battery charger which supplies a $132 V$ d.c. supply using a series resistance of $11.5 Ω$ . What is the terminal voltage of the battery during charging?

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Cells, EMF, Internal Resistance

A car has a fresh storage battery of e.m.f

12 V

and internal resistance

2 \times 10^{- 2} Ω

. If the starter motor draws current of

80 A

. Then the terminal voltage when the starter is on is

While charging a run-down battery, current flows inside it from its negative terminal to positive terminal.

Important Questions on Current Electricity

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