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Current Electricity Calculations Guide

1. This document contains questions about calculating resistance, current, potential difference, internal resistance, and other electrical concepts. 2. Formulas are provided to calculate resistance of wires based on length and diameter, drift velocity of electrons in a conductor, and resistance of hollow conductors. 3. Sample questions ask the learner to calculate equivalent resistance, circuit current, branch currents, internal resistance of a cell, and more based on given values of resistance, current, potential difference, length, diameter, and other variables.

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Ashok Pradhan
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284 views1 page

Current Electricity Calculations Guide

1. This document contains questions about calculating resistance, current, potential difference, internal resistance, and other electrical concepts. 2. Formulas are provided to calculate resistance of wires based on length and diameter, drift velocity of electrons in a conductor, and resistance of hollow conductors. 3. Sample questions ask the learner to calculate equivalent resistance, circuit current, branch currents, internal resistance of a cell, and more based on given values of resistance, current, potential difference, length, diameter, and other variables.

Uploaded by

Ashok Pradhan
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Current electricity

1. Calculate the resistance of eureka wire 1.10m long and 2×10-4m in diameter . Give that specific resistance
=49× 10-8 ohm m Ans: R= 17.15 ohm
2. Show that one ampere is equivalent to a flow of 6.25×1018 elementary charge per second.
3. The amount of charge passing through cross section of a wire is q(t) =at2+bt+c
(i) Write dimension formula for a,b and c
(ii) If the value of a,b and c in SI units are 5,3 and 1 resp. find the current at t=5secind
4. An electric current
5. The P.D. between the terminal of a cell in open circuit , was 2.2 volts and when it is connected through a
resistance of 5 ohm the potential difference fell to 1.8 V. Find the internal resistance of the cell.
Ans: 1.11 ohm
6. Calculate the specific resistance of material wire 1.1 m long and diameter 0.4 mm having total resistance
of 4.2 ohm. Ans: 47.9×10-4 ohm-m.
7. A conductor having cross section of 10-4 m2 carries a current 1.2 A . If the number of free electrons be
5×1028 m-3, calculate the drift velocity of the electrons. Ans: 1.5×10-6 m /s
8. A hollow copper tube of 5 m length has got external diameter equal to 0.1 m and the walls are 5mm thick.
If the resistivity of cupper is 1.7× 10-8 ohm-meter , calculate the resistance of the tube.
Ans: 5.4×10-4 ohm
9. Two resistances of 3 ohm and 2 ohm are in parallel connection and a potential difference of 12 V is applied
across them .Find
(a) Equivalent resistances of parallel combination
(b) The circuit current
(c) The branch current
10. The current i1 ,flows through a circuit when the external resistance is R1 . On changibg the external
resistance R2 , the current becomes i2 , calculate EMF and internal resistance of the source of current.
11. A metal wire of diameter 2 mm and of length 100 m has a resistance of 0.5475 ohm at 200C and 0.805 ohm
at 1500C .Find a resistance of
(a) Temperature coefficient of resistance
(b) Its resistance at 00C
(c) Its resistivity at 00C and 200C Ans: 3.8×10-3?0C , 0.05079Ω 1.596×10-8,1.72×10-6
12. A cell is open circuit has emf of 1.5V .In closed circuit when current is 0.05A , the potential difference
between the poles of the cell is 1.2V .Calculate the internal resistance of the cell. Ans 6V

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