Which of the following equation shows the correct relationship between electrical units ?
1 A = 1 C/s or 1 C = 1 A/s
1A = 1C/s
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.
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.
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) 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 ?
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) 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 ?
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 ?
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 ?
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.
Which of the following resistor arrangement, A or B, has the lower combined resistance ?
A battery of 9 V is connected in series with resistors of 0.2 Ω, 0.3 Ω, 0.4 Ω, 0.5 Ω and 12 Ω. How much current would flow through the 12 Ω resistor ?
An electric bulb of resistance 20 Ω and a resistance wire of 4 Ω are connected in series with a 6 V battery. Draw the circuit diagram and calculate :
(a) total resistance of the circuit.
(b) current through the circuit.
(c) potential difference across the electric bulb.
(d) potential difference across the resistance wire.
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.
How much work is done when one coulomb charge moves against a potential difference of 1 volt ?
Fill in the following blanks with suitable words :
(a) Potential difference is measured in………….. by using a……………. placed in………… across a component.
(b) Copper is a good………….. Plastic is an……………
What is meant by conductors and insulators ? Give two examples of conductors and two of insulators.
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 ?
(a) What do you understand by the term “potential difference” ?
(b) What is meant by saying that the potential difference between two points is 1 volt ?
(c) What is the potential difference between the terminals of a battery if 250 joules of work is required to transfer 20 coulombs of charge from one terminal of battery to the other ?
(d) What is a voltmeter ? How is a voltmeter connected in the circuit to measure the potential difference between two points. Explain with the help of a diagram.
(e) State whether a voltmeter has a high resistance or a low resistance. Give reason for your answer.
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 ?
(a) In which direction does conventional current flow around a circuit ?
(b) In which direction do electrons flow ?
(a) How many milliamperes are there in 1 ampere ?
(b) How many microamperes are there in 1 ampere ?
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.
(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 ?
(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).
Why should the resistance of :
(a) an ammeter be very small ?
(b) a voltmeter be very large ?
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 ?
(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 ?
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 ?
How many electrons are flowing per second past a point in a circuit in which there is a current of 5 amp ?
Name the law which relates the current in a conductor to the potential difference across its ends.
