Advertisements
Advertisements
Question
A cell of e.m.f. 2 V and internal resistance 1.2 Ω is connected to an ammeter of resistance 0.8 Ω and two resistors of 4.5 Ω and 9 Ω as shown in following figure.
Find:
- The reading of the ammeter,
- The potential difference across the terminals of the cells, and
- The potential difference across the 4.5 Ω resistor.
Advertisements
Solution
The total resistance of the circuit is
`"R"_"eq" = "R"_"cell" + "R"_"ammeter" + "R"_1 || "R"_2`
`therefore "R"_"eq" = 1.2 + 0.8 + ("R"_1"R"_2)/("R"_1 + "R"_2)`
`therefore "R"_"eq" = 2 + (4.5 xx 9)/(4.5 + 9)`
= `2 + 40.5/13.5`
`therefore "R"_"eq" = 5 Omega`
(a) Therefore, the current through the ammeter is
I = `"E"_"cell"/"R"_"eq" = 2/5 = 0.4 "A"`
(b) The potential difference across the ends of the cells is
`"V"_"cell" = "E"_"cell" - "IR"_"cell"`
`therefore "V"_"cell" = 2 - 0.4 xx 1.2`
`therefore "V"_"cell" = 2 - 0.48 = 1.52 "V"`
(c) The potential difference across the 4.5 Ω resistor is
`"V"_4.5 = "V"_"cell" - "V"_"ammeter"`
`therefore "V"_4.5 = 1.52 - 0.4 xx 0.8`
`therefore "V"_4.5 = 1.52 - 0.32`
`therefore "V"_4.5 = 1.2 "V"`
APPEARS IN
RELATED QUESTIONS
A cell of Emf 2 V and internal resistance 1.2 Ω is connected with an ammeter of resistance 0.8 Ω and two resistors of 4.5 Ω and 9 Ω as shown in the diagram below:
1) What would be the reading on the Ammeter?
2) What is the potential difference across the terminals of the cell?
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 battery of e.m.f 3.0 V supplies current through a circuit in which the resistance can be changed.
A high resistance voltmeter is connected across the battery. When the current is 1.5 A, the voltmeter reads 2.7 V. Find the internal resistance of the battery.
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 e.m.f. ε and internal resistance 𝔯 sends current 1.0 A when it is connected to an external resistance 1.9 Ω. But it sends current 0.5 A when it is connected to an external resistance 3.9 Ω. Calculate the values of ε and 𝔯.
What is the colour code for the insulation on the earth wire?
Study the diagram:
- Calculate the total resistance of the circuit.
- Calculate the current drawn from the cell.
- State whether the current through 10 Ω resistor is greater than, less than or equal to the current through the 12 Ω resistor.
Explain the meaning of the term internal resistance of a cell.
The diagram in Figure shows a cell of e.m.f. ε = 4 volt and internal resistance r = 2 ohm connected to an external resistance R = 8 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
- the key K is open, and
- the key K is closed
A battery of e.m.f. 6.0 V supplies current through a circuit in which the resistance can be changed. A high resistance voltmeter is connected across the battery. When the current is 3 A, the voltmeter reads 5.4 V. Find the internal resistance of the battery.
