Q1: A charge of 150 C flows through a wire in one minute.
Find the electric current flowing through it.
Q2: The resistance of a wire of 0.01 cm radius is 10 Ω. If
the resistivity of the material of the wire is 50 × 10-8 Ωm, find the length
of wire.
Q3: A circuit has line a line of 5A. How many lamps of
rating 40W; 220V can simultaneously run on this line safely?
Q4: Show four different ways in which four resistors of r Ω
each may be connected in a circuit. In which case is the equivalent resistance
of the combination. (i) maximum (ii) minimum
Q5: Amit lives in Delhi. He is much concerned about the
increasing electricity bill of his house. He took some steps to save
electricity and suceeded in doing so.
(i)
Mention any two steps that Amit might have taken
to save electricity.
(ii)
(ii) Amit
fulfilled his duty towards the environment by saving electricity. How? (iii)
Which alternative source of energy would you suggest Amit to use?
Q6: What is meant by resistance of a conductor? Name and
define its SI unit? List the factors on which the resistance of a conductor
depends. How is the resistance of a wire affected if: (i) its length is
doubled, (ii) its radius is doubled?
Q7: (a) Draw magnetic field lines of a bar magnet.
"Two magnetic field linesnever interact with each other". Why? (b) An
electric oven of 1.5 kW is operated in a domestic circuit (220V) that has a
current rating of 5A. What result do you expect in this case? Explain.
Q8: A
student verifying Ohm's law computed the value of resistance of a resistor for
each set of observation.
However the
values of the resistor were slightly different from the actual value. Is his
experiment wrong? Justify
your answer.
9. Write any one method to induce current in a coil.
10 . The potential difference between the two terminals of
an electric iron is 220 V and the current flowing through its element is 5.0 A.
Calculate the resistance and wattage of the electric iron.
11 . Give reason for the following: (i) Why are copper and
aluminum wires used as connecting wires? (ii) Why is tungsten used for
filaments of electric lamps? (iii) Why is lead tin alloy used for fuse wires ?
12. An electric heater is used on 220 V supply and takes a
current of 5 A. What is its power ? Calculate the per hour cost of using the
heater if 1 unit costs. Rs. 6.0.
13 . A student fixes a sheet of white paper on a drawing
board. He places a bar magnet in the centre of it.
He sprinkles some iron filings uniformly around the bar
magnet. Then he taps the board gently. Now
answer the following questions :
(i) What does the student observe ? Draw a diagram to
illustrate your answer.
(ii) Why do the iron filings arrange in such a pattern ?
(iii) What
does the crowding of the iron filings at the ends of the magnet indicate ?
14 . What is meant by electric circuit ? What is done in
order to have continuous flow of electric charge froma point A to another point
B in an electric circuit ? Write the relation between coulomb and ampere.
Calculate the number of electrons passing per second
through a conductor to produce a current of one ampere. (Charge on electron =
1.6 x 10 -
19 coulomb)
15. What is meant by an
electric circuit?
16. Name, State and
explain with the help of a diagram the rule to find the direction of magnetic
field around a straight conductor carrying current.
17. List two safety
measures commonly used in electric circuits. Explain the main function of each.
24. (a) How does the resistance of a
wire change when- (i) Its length is tripled? (ii) Its radius is tripled?
(iii)Its material is changed to one
whose resistivity is three times?
(b) List two reasons why nichrome is
used for making heatingelement of electrical appliances
18.State how the magnetic
field produced by a straight current carrying conductor at a point depends on
(a) current through the conductor (b) distance of point from conductor.
19.Two lamps, one is
rated 100 W at 200 V and the other 60 W at 220 V, are connected in parallel to
a 220 V supply. Find the current drawn from the supply line.
20.(a) Fuse acts like a
watchman in an electric circuit. Justify this statement. (b) Mention the usual
current rating of the fuse wire in the line to (a) lights and fans (b)
appliance of 2kw or more power.
21.(a) A fuse wire melts
at 5A . If it is desired that the fuse wire of same material melt at 10 A, then
whether the new fuse wire should be of smaller or larger radius than the
earlier one ? Give reasons for your answer.
(b) If the radius of a current carrying
conductor is halved, how does current through it change ?
22.Define resistance of a
conductor. State the factors on which resistance of a conductor depends. Name
the device which is often used to change the resistance without changing the
voltage source in an electric circuit. Calculate the resistance of 50 m length
of wire of cross sectional area of 0.01
square mm and of resistivity 5X10-8Ω.m
