R2 = 10Ω     I2 = ? Question 5. As V2 = I2 R2 = 1 × 10 = 10 volts (b) How much current is flowing through (i) 10 Ω and (it) 15 Ω resistor? You can use above books for extra knowledge and practicing different questions. The resistance of conductor depends on length, thickness, nature of material and temperature of conductor. Question 4. ∴ V = $$\frac{W}{Q}=\frac{100}{20}$$ = 5 Volt Question 3. Question 17. 1 kilowatt-hour = 36,00,000 Joules or 3.6 × 106 J. Resistance, R1 = ? R1 = 10 Ω, R2 = 15 Ω, Voltage = 12 V (iv) ‘The frequency of current in India is 50 Hz’ means the direction of current in India changes 100 times in 1 second as current direction changes twice in one cycle. Thus 4 resistors of 176 Ω in parallel combination are required to carry 5 A on a 220 V line. (CBSE 2012) (CBSE 2008) Iron   10.0 × 10-8 Ωm Question 5. P =VI Required resistance, R2 = 4 Ω; Required length, L2 = ? Resistance, R = ? Lakhmir Singh, Together with CBSE/NCERT Practice Material Chapterwise for Class 10 Science, Mastering Numericals and Objectives of Physics for Class X. Question 2. Answer: Effective resistance, R = R1 + R2 + R3 An electric bulb is rated at 60 W, 240 V. Calculate its resistance. (ii) From the graph, when p.d. An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. When an electric current is passed through a conductor it becomes hot. (i) minimum current flowing, the conductor is directly proportional to the potential difference across its ends. R1 = r + r + r = 3r If you draw a graph between the potential difference and current flowing through a metallic conductor, what kind of curve will you get? Question 20. (iii) Fuse wire is placed in series with the device. Answer: = 0.1 kW × 1 hour = 0.1 kWh. (2012) V = IR ⇒ I = = 1 amp (2013) Answer: In a conductor electrons are flowing from B to A. (2013) (b) How many 176 Ω resistors in parallel are required to carry 5 A on a 220 V line? Answer: Give two reasons why different electrical appliances in a domestic circuit are connected in parallel. (ii) Manganin is used for electrical heating divice as it has the comparatively higher resistivity, less oxidation and variation with temperature. Equivalent resistance of the given network is Answer: An electric iron draws 2.2 amperes of current from a 220 V source. Disadvantages of series circuits for domestic wiring: Question 3. The burning of fossil fuels causes air pollution. Answer: It SI unit is Ampere, electric potential difference is a scalar quantity as it has only magnitude with no direction. (c) (i) Silver is better conductor as its resistivity is less than copper. (d) Calculate the amount of charge flowing through the circuit. (b) List two factors on which resistance of a conductor depends. ∴ V = IR Potential difference between two points is Question 21. Electrical energy consumed, E = P × t Potential difference = 0.5 – 0 = 0.5V (i) Use above graphs to list two differences between the current in the two cases. Copper   1.62 × 10-8 Ωm How would the resistance of the wire change when: The unit of electric charge in the metre–kilogram–second and SI systems is the coulomb and is defined as the amount of electric charge that flows through a cross section of a conductor in an electric circuit during each second when the current has a value of one ampere. Nichrome   100 × 10-6 Ωm. Question 5. (i) directly proportional to the square of current flowing through it, i.e., H ∝ I2. The magnitude and direction of flow of current remains the same. (a) When R1 is connected in series with the parallel combination of R2 and R3 [Fig (a)]. Total potential difference, V = 30 Write relation between heat energy produced in a conductor when a potential difference V is applied across its terminals and a current I flows through for ‘t’. Find the electric current flowing through it. (AI 2008) The resistance of a conductor is defined as the measure of its ability to oppose the flow of electric current through itself. (c) Ammeter reading = Total current flowing through the circuit = 0.5 A. (CBSE 2014) A = $$\frac{\rho l}{\mathrm{R}}$$ The production of hydroelectricity causes ecological imbalance. Define it. I = $$\frac{2000}{220}$$ = 9.09 A. V = 6V I = 0.4 A, Question 1. (CBSE 2008) Draw a labelled circuit diagram to verify this law in the laboratory. Answer: The magnitude and direction of current change continuously at definite intervals of time. (a) Ammeter is used to measure electric current. 40n = 220 × 5 ⇒ n = = 27.5 Resistance of a wire, R = 10 Ω Two lamps, one rated 40W at 220V and the other 100 W at 220V, are connected in parallel to the electric supply at 220V. (a) Voltage is dependent on I and R. Hence, in parallel circuit. (CBSE 2012) (iv) If R1 > R2 > R3 in circuit (I) more heat will be produced in R1 as compared to other two resistors. Calculate the electric energy consumed by 120 W toaster in 20 minutes. (ii) Minimum resistance = Case (b) where all the resistors are combined in parallel combination. Name and define its SI unit. ∴ R’, new resistance = Ω = 2.5 Ω. What is the direction of conventional current? (a) Differentiate between AC and DC. What result is expected? Answer: Resultant resistance of R1, R2 and R3: R’ = R1 + R2 + R3 = 10 + 10 + 10 = 30Ω, Question 19. Question 18. (2015) (a) Differentiate between AC and DC Question 14. Calculate resistance of an electric bulb which allows a 10 A current when connected to 220 V power source. Answer: The voltmeter is always connected in parallel across the conductor. (2012) (a) Two identical resistors each of resistance 10 ohm are connected: (a) Electric power: It is the rate of doing work by an energy source or the rate at which the electrical energy is dissipated or consumed per unit time in the electric circuit is called electric power. (a) State the type of combination of the two resistors in the circuit. All right reserved. and a switch, between the two terminals of a cell or a battery along which an electric current flows is called an electric circuit. It is called alternating current. V = 220 V (c) Name and state the law applicable in the given case. He took some steps to save electricity and succeeded in doing so. Ans: The SI unit of electric power is watt. List the factors on which the resistance of a conductor depends. Answer the following questions in relation to them: Our aim is to help students learn subjects like (AI 2009) The potential difference between two points is said to be 1 volt if 1 joule of work is done in moving 1 coulomb of electric charge from one point to the other.