The main power supply line carries the total current required by all appliances in the house, which can be very high. Thicker wires have lower resistance (R = ρL/A), reducing heat generation (H = I²Rt) and voltage drop, ensuring efficient power delivery. Thinner wires for individual appliances are sufficient because they carry only the current needed by that specific appliance, which is much lower than the total current, and their higher resistance is acceptable for localized connections.
More Questions on Electricity
1An electric heater with a power rating of 2 kW is operated for 3 hours daily for the entire month of April. If the cost of electricity is Rs 6 per unit, what is the total electricity bill for the month? (Assume April has 30 days)
→ 2Assertion (A): Tungsten metal is used for making the filament of incandescent electric lamps. Reason (R): Tungsten has a very high melting point and produces light at high temperatures without melting.
→ 3Two electric bulbs, rated 100W, 220V and 60W, 220V respectively, are connected in series to a 220V supply. Which bulb will glow brighter and why?
→ 4A circuit consists of three resistors: R1, R2, and R3. R1 = 5 Ω is connected in series with the parallel combination of R2 = 10 Ω and R3 = 10 Ω. If this circuit is connected to a 12V battery, what is the power dissipated across R1?
→ 5Explain why household electrical appliances are always connected in parallel with the main supply and not in series.
→ 6Assertion (A): Nichrome alloy is extensively used in the heating elements of electrical appliances like toasters and electric irons. Reason (R): Nichrome has a very high resistivity and a high melting point, making it suitable for producing significant heat without melting.
→ 7An electric heater is rated at 2.2 kW and operates on a 220 V household supply. What is the minimum rating of the fuse that should be used in the circuit to protect the heater?
→ 8A metallic wire of resistance R is stretched uniformly so that its new length becomes twice its original length. Assuming that its volume remains constant during stretching, what will be its new resistance?
→ 9A household circuit consists of two resistors, R1 = 6 Ω and R2 = 3 Ω, connected in parallel. This parallel combination is then connected in series with a third resistor, R3 = 8 Ω. If the entire circuit is connected to a 20 V battery, what is the current flowing through resistor R2?
→ 10The resistance of a circuit component is constant. If the voltage across it is halved, the current through it will:
→ 11The resistance of a conductor is 5 Ohm. If a current of 2A flows through it, the potential difference across its ends is:
→ 12A conductor has 10²0 free electrons passing through a cross-section in 2 seconds. The current flowing is:
→ 13If the voltage across a resistor is 10V and the current flowing is 2A, the power dissipated by the resistor is:
→ 14Which of the following is not a property of electric field lines?
→ 15How many joules are there in 1 calorie?
→ 16The formula for electric energy consumed (E) is:
→ 17A 100W bulb and a 40W bulb are connected in parallel to a 220V supply. Which bulb will glow brighter?
→ 18A 100W bulb and a 40W bulb are connected in series to a 220V supply. Which bulb will glow brighter?
→ 19Which of these is the most suitable material for a heating element?
→ 20What happens to the resistance of a conductor if its area of cross-section is increased?
→ 21The reciprocal of resistance is called:
→ 22In a parallel circuit, if one bulb fuses, the other bulbs:
→ 23In a series circuit, if one bulb fuses, the other bulbs:
→ 24Which combination of resistors provides the lowest equivalent resistance?
→ 25An electric iron of 1000 W is used for 2 hours daily. If the cost of 1 unit of electricity is Rs. 5, what is the cost of using the iron for 30 days?
→ 26What is the equivalent resistance of three 6 Ohm resistors connected in parallel?
→ 27What is the total power consumed by two lamps rated 60W and 40W, respectively, when connected in parallel across a 220V supply?
→ 28The resistance of a wire is R. If it is stretched to twice its original length, its new resistance will be:
→ 29If the current through a resistor is doubled, the heat produced in a given time interval will:
→ 30A 2 Ohm resistor carries a current of 3 A. The heat produced in 10 seconds is:
→ 31Which of the following is an ohmic conductor?
→ 32If the temperature of a semiconductor increases, its resistance:
→ 33The direction of electron flow is ___________ to the conventional current.
→ 34The energy supplied by the cell in moving a unit charge from one end to the other is called its:
→ 35What is the cause of 'overloading' in domestic circuits?
→ 36What does a 'short circuit' mean in an electric circuit?
→ 37The symbol for a variable resistor is:
→ 38Why are copper wires generally used for electrical transmission?
→ 39If an electric bulb of 40W, 220V is connected to a 110V supply, the power consumed will be:
→ 40Which statement is true for voltage in a parallel circuit?
→ 41Which statement is true for current in a series circuit?
→ 42A device that changes the resistance in an electric circuit is called a:
→ 43The material of an electric fuse wire should have:
→ 44What is the effect of increasing temperature on the resistance of a pure metal conductor?
→ 45An electric cell converts:
→ 46Which of the following is true about electric potential?
→ 47The property of a conductor to resist the flow of current is called:
→ 48In a parallel circuit containing two resistors, if the current through the first resistor is 2 A and the total current is 5 A, what is the current through the second resistor?
→ 49A circuit consists of two resistors in series. If the voltage across the first resistor is 5 V and the total voltage is 12 V, what is the voltage across the second resistor?
→ 50If an electric bulb draws a current of 0.5 A when the voltage is 200 V, its power is:
→ 51If the reading of an ammeter is 2 A and the resistance is 10 Ohm, what is the voltage across the resistor?
→ 52A 60 W light bulb is switched on for 2 hours. How much electrical energy is consumed?
→ 53Which of the following represents electric power?
→ 54To increase the brightness of a bulb in a circuit, we can:
→ 55The resistance of an ideal voltmeter is:
→ 56The resistance of an ideal ammeter is:
→ 57Why is tungsten used for the filament of incandescent light bulbs?
→ 58Which material is typically used for heating elements in electric toasters and irons?
→ 59A component whose resistance changes with voltage is called a:
→ 60A current of 2 A flows through a conductor for 5 minutes. The amount of charge that passes through the conductor is:
→ 61The amount of current flowing through a circuit is 0.5 A. How much charge passes through a point in the circuit in 10 minutes?
→ 62If 100 J of work is done to move 4 C of charge from one point to another, the potential difference between the two points is:
→ 63What is the potential difference required to make 1 A of current flow through a resistance of 1 Ohm?
→ 64Which of the following is a good conductor of electricity?
→ 65The 'Ampere' is the unit of:
→ 66The unit 'Volt' is equivalent to:
→ 67An electric heater is rated 1500 W, 220 V. The current drawn by it is:
→ 68Two resistors of 10 Ohm and 20 Ohm are connected in parallel. The equivalent resistance is:
→ 69Two resistors of 10 Ohm and 20 Ohm are connected in series. The equivalent resistance is:
→ 70Resistivity of a conductor depends on:
→ 71The resistance of a conductor is inversely proportional to its:
→ 72How many electrons constitute one coulomb of charge?
→ 73What is the charge of an electron?
→ 74In an electric circuit, the conventional direction of current flow is:
→ 75A 220 V, 100 W bulb has a resistance of approximately:
→ 76Which of the following factors does not affect the resistance of a conductor?
→ 77When the cross-sectional area of a metallic wire is doubled, its resistance will:
→ 78When the length of a metallic wire is doubled, its resistance will:
→ 79If a wire of resistance R is cut into two equal halves, the resistance of each half will be:
→ 80Why are domestic electrical appliances usually connected in parallel?
→ 81The material used for the filament of an electric bulb is usually:
→ 82An electric fuse is used as a safety device in circuits to:
→ 831 kilowatt-hour is equivalent to:
→ 84The commercial unit of electrical energy is:
→ 85The SI unit of electric power is:
→ 86The rate at which electrical energy is consumed or dissipated in an electric circuit is called:
→ 87Which of the following is an application of the heating effect of electric current?
→ 88The heating effect of electric current is given by:
→ 89When resistors are connected in parallel, the reciprocal of the total resistance is equal to:
→ 90When resistors are connected in series, the total resistance is:
→ 91Which of the following materials has the lowest electrical resistivity?
→ 92The SI unit of electrical resistance is:
→ 93The resistance of a conductor depends on:
→ 94According to Ohm's Law, if the potential difference across a conductor is doubled, the current flowing through it will:
→ 95Ohm's Law states the relationship between:
→ 96A device used to measure potential difference across two points in an electric circuit is called:
→ 97The SI unit of potential difference is:
→ 98The work done in moving a unit charge from one point to another in an electric circuit is called:
→ 99A device used to measure electric current in a circuit is called:
→ 100The SI unit of electric current is:
→ 101The flow of electric charge is known as:
→ 102Which of the following is an example of an electrical insulator?
→ 103The SI unit of electric charge is:
→ 104What determines the rate at which energy is delivered by a current?
→ 105An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.
→ 106Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50 V
→ 107Why does the cord of an electric heater not glow while the heating element does?
→ 108What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?
→ 109Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
→ 110Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?
→ 111Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
→ 112On what factors does the resistance of a conductor depend?
→ 113What is meant by saying that the potential difference between two points is 1 V?
→ 114Name a device that helps to maintain a potential difference across a conductor.
→ 115Calculate the number of electrons constituting one coulomb of charge.
→ 116Define the unit of current.
→ 117What does an electric circuit mean?
→ 118How much energy is given to each coulomb of charge passing through a 6 V battery?
→ 119What is the maximum resistance which can be made using five resistors each of 1/5 Ω ?
→ 120A current of 1 A is drawn by a filament of an electric bulb. Number of electrons passing through a cross section of the filament in 16 seconds would be roughly.
→ 121Calculate the resistivity of the material of a wire of length 1 m, radius 0.01 cm and resistance 20 ohms.
→ 122List the factors on which the resistance of a conductor in the shape of a wire depends.
→ 123Why are alloys commonly used in electrical heating devices ?
→ 124Why are metals good conductors of electricity whereas glass is a bad conductor of electricity ? Give reason.
→ 125Calculate the resistance of a metal wire of length 2 meters and cross-sectional area 1.55 × 10⁻⁶ square meters, if the resistivity of the metal is 2.8 × 10⁻⁸ ohm meter.
→ 126How is the resistivity of alloys compared with those of pure metals from which they may have been formed?
→ 127Name a device that you can use to maintain a potential difference between the ends of a conductor. Explain the process by which this device does so.
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