Advertisements
Advertisements
प्रश्न
Two cells of same emf E but internal resistance r1 and r2 are connected in series to an external resistor R (Figure). What should be the value of R so that the potential difference across the terminals of the first cell becomes zero.
Advertisements
उत्तर
In this problem first we apply Ohm' law to find current in the circuit.
Effective emf of two cells = E + E = 2E
Effective resistance = R + r1 + r2
So the electric current is given by
`I = (E + E)/(R + r_1 + r_2)`
`V_1 = E - Ir_1 = E - (2E.r_1)/(R + r_1 + r_2)`
The net potential difference across 1st cell V1 = 0 (Given)
∴ `E - (2Er_1)/(R + r_1 + r_2)` = 0
Or `1 - (2r_1)/(R + r_1 + r_2)` = 0
`(2r_1)/(r_1 + r_2 + R) = 1/1`
Or 2r1 = r1 + r2 + R
| r1 – r2 = R |
It is the required condition for the potential difference across 1st cell to be zero.
APPEARS IN
संबंधित प्रश्न
If the potential difference across the ends of a conductor is 220 V and the resistance of the conductor is 44 Ω (ohm), then the current flowing through is _________.
- 0.2 A
- 0.5 A
- 2 A
- 5 A
What will be the change in the current if the potential difference is kept constant and the resistance of the circuit is made four times?
- It will remain unchanged.
- It will become four times.
- It will become one-fourth.
- It will become half.
The graph between V and I for a conductor is a straight line passing through the origin.
- Which law is illustrated by such a graph?
- What should remain constant in a statement of this law?
The resistors R1, R2, R3 and R4 in the figure given below are all equal in value.
What would you expect the voltmeter A, B and C to read assuming that the connecting wires in the circuit have negligible resistance?
How much energy is consumed when a current of 5 amperes flows through the filament (or element) of a heater having resistance of 100 ohms for two hours? Express it in joules.
In a conductor 6.25 × `10^16` electrons flow from its end A to B in 2 s. Find the current flowing through the conductor (e = 1.6 × `10^-19` C)
An electric bulb draws 1.2 A current at 6.0 V. Find the resistance of filament of bulb while glowing.
In an experiment of verification of Ohm’s law following observations are obtained.
|
Potential difference V (in volt) |
0.5 | 1.0 | 1.5 | 2.0 | 2.5 |
| current I (in ampere) | 0.2 | 0.4 | 0.6 | 0.8 | 1.0 |
Draw a V-I graph and use this graph to find:
- the potential difference V when the current I is 0.5 A,
- the current I when the potential difference V is 0.75 V,
- the resistance in a circuit.
A wire of resistance 9 ohm having length 30 cm is tripled on itself. What is its new resistance?
Tick(✓) the correct choice in the following:
Ohm's law is applicable to
- Name and state the law which relates the potential difference and current in a conductor.
- What is the necessary condition for a conductor to obey the law named above in part (a) ?
What is non-ohmic resistor?
Draw a neat diagram for the verification of Ohm’s law by voltmeter-ammeter method. By another diagram show the relation between p.d. and current.
Choose the correct alternative.
Which of the following is an ohmic conductor?
A current of 2amp flowing through a conductor produced 80 joule of heat in 10 sec. The resistance of the conductor is:-
The heat produced by a 100 w heater in 2 minute is equal to
Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is ______.
Suppose there is a circuit consisting of only resistances and batteries and we have to double (or increase it to n-times) all voltages and all resistances. Show that currents are unaltered. Do this for circuit of Example 3.7 in the NCERT Text Book for Class XII.
Vinita and Ahmed demonstrated a circuit that operates the two headlights and the two sidelights of a car, in their school exhibition. Based on their demonstrated circuit, answer the following questions.
- State what happens when switch A is connected to:
a) Position 2
b) Position 3 - Find the potential difference across each lamp when lit.
- Calculate the current.
a) in each 12 Ω lamp when lit.
b) In each 4 Ω lamp when lit.
OR - Show, with calculations, which type of lamp, 4.0 Ω or 12 Ω, has the higher power.
