Physics

Electricity

Question:

(a) In which direction does conventional current flow around a circuit ?
(b) In which direction do electrons flow ?

Answer:

(a) Conventional current flows from positive terminal of a battery to the negative terminal, through the outer circuit.
(b) Electrons flow from negative terminal to positive terminal of the battery (opposite to the direction of conventional current).

 

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Electricity

Q 1.

Compare how an ammeter and a voltmeter are connected in a circuit.

Q 2.

What is an ammeter ? How is it connected in a circuit ? Draw a diagram to illustrate your answer.

Q 3.

Which among iron and mercury is a better conductor of electricity ?

Q 4.

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 ?

Q 5.

What is the unit of electric charge ?

Q 6.

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 ?

Q 7.

Name the material which is the best conductor of electricity.

Q 8.

Keeping the resistance constant, the potential difference applied across the ends of a component is halved. By how much does the current change ?

Q 9.

Keeping the potential difference constant, the resistance of a circuit is halved. By how much does the current change ?

Q 10.

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.

Q 11.

Name the material which is used for making the heating element of an electric iron.

Q 12.

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.

Q 13.

By what name is the physical quantity coulomb/second called ?

Q 14.

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…………

Q 15.

Find the current in each resistor in the circuit shown below :
lakhmir-singh-physics-class-10-solutions-electricity-38(12)

Q 16.

(a) What do the letters p.d. stand for ?
(b) Which device is used to measure p.d. ?

Q 17.

(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 ?

Q 18.

What do the following symbols mean in circuit diagrams ?
lakhmir-singh-physics-class-10-solutions-electricity-1

Q 19.

Name the law which relates the current in a conductor to the potential difference across its ends.

Q 20.

On what factors does the resistance of a conductor depend ?

Q 21.

The electrical resistivities of four materials A, B, C and D are given below :
Untitled
Which material is : (a) good conductor (b) resistor (c) insulator, and (d) semiconductor ?

Q 22.

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 ?

Q 23.

What is the SI unit of potential difference ?

Q 24.

What do you understand by the term “electric potential” ? (or potential) at a point ? What is the unit of electric potential ?

Q 25.

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.

Q 26.

(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 ?

Q 27.

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 ?

Q 28.

The electrical resistivities of three materials P, Q and R are given below :
Untitled
Which material will you use for making (a) electric wires (b) handle for soldering iron, and (c) solar cells ? Give reasons for your choices.

Q 29.

Give the law of combination of resistances in series.

Q 30.

If 3 resistances of 3 ohm each are connected in parallel, what will be their total resistance ?

Q 31.

Show how you would connect two 4 ohm resistors to produce a combined resistance of
(a) 2 ohms
(b) 8 ohms.

Q 32.

What is meant by conductors and insulators ? Give two examples of conductors and two of insulators.

Q 33.

What actually travels through the wires when you switch on a light ?

Q 34.

Which particles constitute the electric current in a metallic conductor ?

Q 35.

If 20 C of charge pass a point in a circuit in 1 s, what current is flowing ?

Q 36.

(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 ?

Q 37.

(a) What is an electric current ? What makes an electric current flow in a wire ?
(b) Define the unit of electric current (or Define ampere).

Q 38.

Name the unit of electrical resistance and give its symbol.

Q 39.

A potential difference of 20 volts is applied across the ends of a resistance of 5 ohms. What current will flow in the resistance ?

Q 40.

Distinguish between good conductors, resistors and insulators. Name two good conductors, two resistors and two insulators.

Q 41.

(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 :
lakhmir-singh-physics-class-10-solutions-electricity-4
(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 ?

Q 42.

A current of 200 mA flows through a 4 kΩ resistor. What is the p.d. across the resistor ?

Q 43.

What happens to the resistance as the conductor is made thicker ?

Q 44.

If the length of a wire is doubled by taking more of wire, what happens to its resistance ?

Q 45.

Why are copper and aluminium wires usually used for electricity transmission ?

Q 46.

Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.

Q 47.

Why are the coils of electric irons and electric toasters made of an alloy rather than a pure metal ?

Q 48.

(a) Write down an expression for the resistance of a metallic wire in terms of the resistivity.
What will be the resistance of a metal wire of length 2 metres and area of cross-section 1.55 × 10-6 m2, if the resistivity of the metal be 2.8 × 10-8 Ωm ?

Q 49.

(a) Give two examples of substances which are good conductors of electricity. Why do you think they are
good conductors of electricity ?
Calculate the resistance of a copper wire 1.0 km long and 0.50 mm diameter if the resistivity of copper is 1.7 × 10-8 Ωm.

Q 50.

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 ?