What is the general name of the substances having infinitely high electrical resistance ?
Insulators.
How should the two resistances of 2 ohms each be connencted so as to produce an equivalent resistance of 1 ohm ?
Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.
(a) How many milliamperes are there in 1 ampere ?
(b) How many microamperes are there in 1 ampere ?
Why are the coils of electric irons and electric toasters made of an alloy rather than a pure metal ?
In 10 s, a charge of 25 C leaves a battery, and 200 j of energy are delivered to an outside circuit as a result.
(a) What is the p.d. across the battery ?
(b) What current flows from the battery ?
(a) In which direction does conventional current flow around a circuit ?
(b) In which direction do electrons flow ?
A student made an electric circuit shown here to measure the current through two lamps.
(a) Are the lamps in series or parallel ?
(b) The student has made a mistake in this circuit.
What is the mistake ?
(c) Draw a circuit diagram to show the correct way to connect the circuit.
Use the proper circuit symbols in your diagram.
(a) Give one example to show how the resistance depends on the nature of material of the conductor.
(b) Calculate the resistance of an aluminium cable of length 10 km and diameter 2.0 mm if the resistivity of aluminium is 2.7 x 10-8Ωm.
A resistance of 20 ohms has a current of 2 amperes flowing in it. What potential difference is there between its ends ?
Show how you would connect two 4 ohm resistors to produce a combined resistance of
(a) 2 ohms
(b) 8 ohms.
The electrical resistivities of four materials A, B, C and D are given below :
Which material is : (a) good conductor (b) resistor (c) insulator, and (d) semiconductor ?
(a) Name a device that helps to measure the potential difference across a conductor.
(b) How much energy is transferred by a 12 V power supply to each coulomb of charge which it moves around a circuit ?
The electrical resistivities of five substances A, B, C, D and E are given below :
A 5.20 x l0-8 Ω m
How should the two resistances of 2 ohms each be connencted so as to produce an equivalent resistance of 1 ohm ?
(a) Name a device which helps to maintain potential difference across a conductor (say, a bulb).
If a potential difference of 10 V causes a current of 2 A to flow for 1 minute, how much energy is
transferred ?
If the charge on an electron is 1.6 x 10-19 coulombs, how many electrons should pass through a conductor in 1 second to constitute 1 ampere current ?
The graph between V and 1 for a conductor is a straight line passing through the origin.
Which law is illustrated by such a graph ?
What should remain constant in a statement of this law ?
How does the resistance of a wire vary with its :
(a) area of cross-section ?
(b) diameter ?
How does the resistance of a wire change when :
(i) its length is tripled ?
(ii) its diameter is tripled ?
(in) its material is changed to one whose resistivity is three times ?
What possible values of resultant resistance one can get by combining two resistances, one of value 2 ohm and the other 6 ohm ?
Three resistors are connected as shown in the diagram.
Through the resistor 5 ohm, a current of 1 ampere is flowing,
(i) What is the current through the other two resistors ?
(ii) What is the p.d. across AB and across AC ?
(iii) What is the total resistance ?
Which of the following equation shows the correct relationship between electrical units ?
1 A = 1 C/s or 1 C = 1 A/s
What is an ammeter ? How is it connected in a circuit ? Draw a diagram to illustrate your answer.
How many electrons are flowing per second past a point in a circuit in which there is a current of 5 amp ?
What is the general name of the substances having infinitely high electrical resistance ?
A potential difference of 20 volts is applied across the ends of a resistance of 5 ohms. What current will flow in the resistance ?
Distinguish between good conductors, resistors and insulators. Name two good conductors, two resistors and two insulators.
(a) Why do electricians wear rubber hand gloves while working with electricity ?
(b) What p.d. is needed to send a current of 6 A through an electrical appliance having a resistance of 40 Ω ?
How does the resistance of a conductor depend on :
(a) length of the conductor ?
(b) area of cross-section of the conductor ?
(c) temperature of the conductor ?
What would be the effect on the resistance of a metal wire of :
(a) increasing its length ?
(b) increasing its diameter ?
(c) increasing its temperature ?
A piece of wire of resistance 20 Ω is drawn out so that its length is increased to twice its original length. Calculate the resistance of the wire in the new situation.
A wire that has resistance R is cut into two equal pieces. The two parts are joined in parallel. What is the resistance of the combination ?
What do you understand by the term “electric potential” ? (or potential) at a point ? What is the unit of electric potential ?
The atoms of copper contain electrons and the atoms of rubber also contain electrons. Then why does copper conduct electricity but rubber does not conduct electricity ?
