Page 1 - Home Assignment

HOME ASSIGNMENT-(Current electricity)
1 If n,e,τ and m represent electron density,charge ,relaxation time and mass of an electron ,then the
resistance of the wire of length l and cross-sectional area A is:
2
(a)ml/ne τ A
2
(b)mΤa/ne l
2
(c)ne τA/ml
2
(d)ne ml/ τA
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2 Dimensions of a block are 1 cm x 1 cm x 100 cm .If specific resistance of its material is 3 x 10 Ωm,
then the resistance between the opposite rectangular faces is :
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(a)3 x 10 Ω (b)3 x 10 Ω (c)3 x 10 Ω (d)3 x 10 Ω
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6 To get maximum current in a resistance of 3 Ω ,one can use m rows of n cells each (connected in
series), connected in parallel. If the total number of cells is 24 and the internal resistance of a cell
is 0.5 Ω, then:
(a)m=12,n=2 (b)m=8,n=3 (c)m=2,n=12 (d)m=6,n=4
7 Three identical cells, each of emf 4 V and internal resistance r, are connected in series to a 6 Ω
resistor. If the current flowing in the circuit is 2 A. The internal resistance of each cell is:
(a)0.11 Ω (b)5 Ω (c)0.12 Ω (d)none of these
8 Six lead acid type of secondary cells , each of emf 2 V and internal resistance 0.015 Ω, are joined in
series to provide a supply to resistance of 8.5 Ω.The current drawn from the supply is__________.
9 A cell of emf E and resistance r is connected across an external resistance R. the potential
difference across the terminals of a cell for r =R is _______________.
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10 A car has a fresh storage battery ofemf 12 V and internal resistance 5 x 10 Ω. If the starter
motor draws a current of 90 A, then the terminal voltage of the battery when the starter is on
is_______
11 Current density is a___________ quantity.
12 The current flowing through a conductor is 2 mA at 50 V and 3 mA at 60 V.It is___________
(ohmic/non-ohmic )conductor.
13 Commercial unit of electric energy is____________________
14 State Joule’s law of heating.
15 Calculate the current drawn from the battery by the network of resistors shown in the figure.