Advertisements
Advertisements
प्रश्न
A cell supplies a current of 0.6 A through a 2Ω coil and a current of 0.3 A through on 8Ω coil. Calculate the e.m.f and internal resistance of the cell.
Advertisements
उत्तर
Given: I1 = 0.6 A, R1 = 2 Ω and I2 = 0.3 A, R2 = 8 Ω
Let the e.m.f. of the cell is E and its internal resistance is r.
From I = `"E"/("R + r")`
0.6 = `"E"/("2 + r")` and `0.3 = "E"/("8 + r")`
∴ E = 0.6 (2 + r) = 1.2 + 0.6 r and
E = 0.3 (8 + r) = 2.4 + 0.3r
Thus, 1.2 + 0.6r = 2.4 + 0.3r
or 0.6r - 0.3r = 2.4 - 1.2
Or 0.3 r = 1.2 or
r = `1.2/0.3 = 4 Omega`.
and E = 1.2 + 0.6 × 4 = 1.2 + 2.4 = 3.6 V
संबंधित प्रश्न
Name two factors on which the internal resistance of a cell depends and state how does it depend on the factors stated by you.
A cell of e.m.f ε and internal resistance r is used to send current to an external resistance R. Write expressions for
- the total resistance of circuit.
- the current drawn from the cell.
- the p.d. across the cell.
- voltage drop inside the cell.
Explain why the p.d across the terminals of a cell is more in an open circuit and reduced in a closed circuit.
A cell is used to send current to an external circuit.
- How does the voltage across its terminals compare with its e.m.f.?
- Under what condition is the e.m.f. of a cell equal to its terminal voltage?
The diagram below in Fig. 8.40 shows a cell of e.m.f. ε = 2 volt and internal resistance r = 1 ohm to an external resistance R = 4 ohm. The ammeter A measures the current in the circuit and the
voltmeter V measures the terminal voltage across the cell. What will be the readings of the ammeter and voltmeter when (i) the key K is open, (ii) the key K is closed.
A cell of e.m.f. 1.8V and internal resistance 2Ω is connected in series with an ammeter of resistance 0.7Ω and a resistor of 4.5Ω as shown in Fig.
- What would be the reading of the ammeter?
- What is the potential difference across the terminals of the cell?
A cell of emf. 1.5 V and internal resistance 10 ohms is connected to a resistor of 5 ohms, with an ammeter in series see fig.. What is the reading of the ammeter?
Define the e.m.f. (E) of a cell and the potential difference (V) of a resistor R in terms of the work done in moving a unit charge. State the relation between these two works and the work done in moving a unit charge through a cell connected across the resistor. Take the internal resistance of the cell as ‘r’. Hence obtain an expression for the current i in the circuit.
A battery of 4 cell, each of e.m.f. 1.5 volt and internal resistance 0.5 Ω is connected to three resistances as shown in the figure. Calculate:
(i) The total resistance of the circuit.
(ii) The current through the cell.
(iii) The current through each resistance.
(iv) The p.d. across each resistance.
When a resistance of 3Ω is connected across a cell, the current flowing is 0.5 A. On changing the resistance to 7Ω, the current becomes 0.25A. Calculate the e.m.f. and the internal resistance of the cell.
