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
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
Name the physical quantity whose unit is "ohm".
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)
A wire of resistance 3 ohm and length 10 cm is stretched to length 30 cm. Assuming that it has a uniform cross section, what will be its new resistance?
Calculate the electric field in a copper wire of cross-sectional area 2.0 mm2 carrying a current of 1 A.
The resistivity of copper = 1.7 × 10–8 Ω m
A wire has a length of 2.0 m and a resistance of 5.0 Ω. Find the electric field existing inside the wire if it carries a current of 10 A.
Calculate the effective resistance across AB?
Fig. represents the circuit used for the verification of ohm's law. Label the different parts from A and F. State the function of each.
Define the following:
Coulomb
Fig. represents the circuit used for the verification of Ohm's law. Label the parts from A to F. state the function of each.
Rewrite the following statement by selecting the correct option.
The S.I. unit of resistance is __________.
What is non-ohmic resistor?
An ammeter placed in series with an electric radiator reads 0.5 amps and a voltmeter placed across it reads 230 volts. What is the resistance of the radiator?
Define Current density.
Two cells each of 5V are connected in series across an 8Ω resistor and three parallel resistors of 4Ω, 6Ω, and 12Ω. Draw a circuit diagram for the above arrangement. Calculate
- the current drawn from the cell
- current through each resistor
Which of the following is correct for V-I graph of a good conductor?
The slope of voltage (V) versus current (I) is called:
The variable resistance is called ____________.
Why should an ammeter have low resistance?
The voltage - current readings of a certain material are shown in the table given below:
| Voltage (V) | 10 V | 20 V | 30 V |
| Current (I) | 2 A | 3 A | 4 A |
Study the table.
- State whether the conductor used is ohmic or non-ohmic.
- Justify your answer.
- State Ohm's law.
