By what other name is the unit joule/coulomb called ?
Volt
What is an ammeter ? How is it connected in a circuit ? Draw a diagram to illustrate your answer.
Keeping the resistance constant, the potential difference applied across the ends of a component is halved. By how much does the current change ?
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 ?
State the factors on which the strength of electric current flowing in a given conductor depends.
Fill in the following blanks with suitable words :
(a) A current is a flow of……….. For this to happen there must be a………….
(b) Current is measured in……… using an………… placed in……… in a circuit.
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 p.d. across a lamp is 12 V. How many joules of electrical energy are changed into heat and light when :
(a) a charge of 1 C passes through it ?
(b) a charge of 5 C passes through it ?
(c) a current of 2 A flows through it for 10 s ?
Draw a circuit diagram to show how 3 bulbs can be lit from a battery so that 2 bulbs are controlled by the same switch while the third bulb has its own switch.
An electric heater is connected to the 230 V mains supply. A current of 8 A flows through the heater.
(a) How much charge flows around the circuit each second ?
(b) How much energy is transferred to the heater each second ?
(a) Define the unit of resistance (or Define the unit “ohm”).
What happens to the resistance as the conductor is made thinner ?
Keeping the potential difference constant, the resistance of a circuit is doubled. By how much does the current change ?
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 ?
Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.
Why are the coils of electric irons and electric toasters made of an alloy rather than a pure metal ?
Fill in the following blanks with suitable words :
Resistance is measured in…………….. The resistance of a wire increases as the length…………………. ; as the
temperature………. ; and as the cross-sectional area…………
How does the resistance of a wire vary with its :
(a) area of cross-section ?
(b) diameter ?
If five resistances, each of value 0.2 ohm, are connected in series, what will be the resultant resistance ?
What possible values of resultant resistance one can get by combining two resistances, one of value 2 ohm and the other 6 ohm ?
For the circuit shown in the diagram below :
What is the value of :
(i) current through 6 Ωresistor ?
(ii) potential difference across 12 Ω resistor ?
How much work is done when one coulomb charge moves against a potential difference of 1 volt ?
What do you understand by the term “electric potential” ? (or potential) at a point ? What is the unit of electric potential ?
(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 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 ?
Which of the following equation shows the correct relationship between electrical units ?
1 A = 1 C/s or 1 C = 1 A/s
A current of 4 A flows around a circuit for 10 s. How much charge flows past a point in the circuit in this time ?
Why should the resistance of :
(a) an ammeter be very small ?
(b) a voltmeter be very large ?
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) Define electric current. What is the SI unit of electric current.
(b) One coulomb of charge flows through any cross-section of a conductor in 1 second. What is the current flowing through the conductor ?
(c) Which instrument is used to measure electric current ? How should it be connected in a circuit ?
(d) What is the conventional direction of the flow of electric current ? How does it differ from the direction of flow of electrons ?
(e) A flash of lightning carries 10 C of charge which flows for 0.01 s. What is the current ? If the voltage is 10 MV, what is the energy ?
Name the law which relates the current in a conductor to the potential difference across its ends.
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 ?
A resistance of 20 ohms has a current of 2 amperes flowing in it. What potential difference is there between its ends ?
(a) What is meant by the “resistance of a conductor” ? Write the relation between resistance, potential
difference and current.
(b) When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Calculate the value of the resistance of the resistor.
(a) What is the ratio of potential difference and current known as ?
(b) The values of potential difference V applied across a resistor and the corresponding values of current I
flowing in the resistor are given below :
(c) Name the law which is illustrated by the above V-I graph.
(d) Write down the formula which states the relation between potential difference, current and resistance,
(e) The potential difference between the terminals of an electric iron is 240 V and the current is 5.0 A. What is the resistance of the electric iron ?
A current of 200 mA flows through a 4 kΩ resistor. What is the p.d. across the resistor ?
If the length of a wire is doubled by taking more of wire, what happens to its resistance ?
(a) How does the resistance of a pure metal change if its temperature decreases ?
(b) How does the presence of impurities in a metal affect its resistance ?
