Name the electrical property of a material whose symbol is “omega”.
Why are the coils of electric irons and electric toasters made of an alloy rather than a pure metal ?
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 ?
If 3 resistances of 3 ohm each are connected in parallel, what will be their total resistance ?
What is meant by saying that the electric potential at a point is 1 volt ?
What happens to the resistance as the conductor is made thicker ?
How does the resistance of a wire vary with its :
(a) area of cross-section ?
(b) diameter ?
(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 ?
Compare how an ammeter and a voltmeter are connected in a circuit.
A p.d. of 10 V is needed to make a current of 0.02 A flow through a wire. What p.d. is needed to make a current of 250 mA flow through the same wire ?
How much work is done in moving a charge of 2 C across two points having a potential difference of 12 V ?
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 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
A potential difference of 20 volts is applied across the ends of a resistance of 5 ohms. What current will flow in the resistance ?
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 ?
(a) What do the letters p.d. stand for ?
(b) Which device is used to measure p.d. ?
Will current flow more easily through a thick wire or a thin wire of the same material when connected to the same source ? Give reason for your answer.
Which of the following statements correctly defines a volt ?
(a) a volt is a joule per ampere.
(b) a volt is a joule per coulomb.
What is meant by conductors and insulators ? Give two examples of conductors and two of insulators.
Which particles constitute the electric current in a metallic conductor ?
What is the unit of electric charge ?
If 20 C of charge pass a point in a circuit in 1 s, what current is flowing ?
What is nichrome ? State its one use.
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 ?
What actually travels through the wires when you switch on a light ?
(a) In which direction does conventional current flow around a circuit ?
(b) In which direction do electrons flow ?
The electrical resistivities of three materials P, Q and R are given below :
Which material will you use for making (a) electric wires (b) handle for soldering iron, and (c) solar cells ? Give reasons for your choices.
A current of 5 amperes flows through a wire whose ends are at a potential difference of 3 volts. Calculate the resistance of the wire.
Fill in the following blank with a suitable word :
Ohm’s law states a relation between potential difference and……………………
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…………
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 is the SI unit of potential difference ?
Why should the resistance of :
(a) an ammeter be very small ?
(b) a voltmeter be very large ?
How many electrons are flowing per second past a point in a circuit in which there is a current of 5 amp ?
Show how you would connect two 4 ohm resistors to produce a combined resistance of
(a) 2 ohms
(b) 8 ohms.
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 ?
Name the law which relates the current in a conductor to the potential difference across its ends.
Keeping the resistance constant, the potential difference applied across the ends of a component is halved. By how much does the current change ?
Keeping the potential difference constant, the resistance of a circuit is halved. By how much does the current change ?
Name the material which is used for making the heating element of an electric iron.
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 ?
Which of the two is connected in series : ammeter or voltmeter ?
(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 ?
Name the unit of electrical resistance and give its symbol.
What is Ohm’s law ? Explain how it is used to define the unit of resistance.
On what factors does the resistance of a conductor depend ?
Give the law of combination of resistances in series.
What is the current in a circuit if the charge passing each point is 20 C in 40 s ?
What is an ammeter ? How is it connected in a circuit ? Draw a diagram to illustrate your answer.
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 ?
State the factors on which the strength of electric current flowing in a given conductor depends.