Electricity: Class 10 Science Q&A · Page 14
281 free answers on Electricity (Science) for Class 10 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ScienceClass 10CBSE
Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be _____. (a) 1:2 (b) 2:1 (c) 1:4 (d) 4:1
Solution: Let Rs and Rp be the equivalent resistance of the wires when connected in series and parallel respectively. For the same potential difference V, the ratio of the heat produced in the circuit is given by Hence, the ratio of the heat produced is 1:4.
- ScienceClass 10CBSE
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be _____. (a) 100 W (b) 75 W (c) 50 W (d) 25 W
Answer: 25 W Explanation: The energy consumed by the appliance is given by the expression P = VI = V2/R The resistance of the light bulb can be calculated as follows: R = V2/P Substituting the values, we get R = (220)2/100 = 484 Ω Even if the supply voltage is reduced, the resistance remains the same. Hence, the power consumed can be calculated as follows:</p
- ScienceClass 10CBSE
Which of the following does not represent electrical power in a circuit? (a) I2R (b) IR2 (c) VI (d) V2/R
Answer: b) IR2 Explanation: Electrical power is given by the expression P = VI. (1) According to Ohm’s law, V = IR Substituting the value of V in (1), we get P = (IR) × I P = I2R Similarly, from Ohm’s law, I =&n
- ScienceClass 10CBSE
A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R′, then the ratio R/R′ is _____. (a) 1/25 (b) 1/5 (c) 5 (d) 25
Solution: Answer: d) 25 Explanation: The resistance is cut into five equal parts, which means that the resistance of each part is R/5. We know that each part is connected to each other in parallel, hence the equivalent resistance can be calculated as follows: The ratio of R/R′ is 25.
- ScienceClass 10CBSE
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Solution: The power of the motor can be calculated by the equation, P = VI Substituting the values in the above equation, we get P = 220 V × 5 A = 1100 W The energy consumed by the motor can be calculated using the equation, E = P × T Substituting the values in the above equation, we get P = 1100 W × 7200 = 7.92 × 106 J The power of the motor is 1100 W an
- ScienceClass 10CBSE
What determines the rate at which energy is delivered by a current?
Solution: Electric power is the rate of consumption of electrical energy by electric appliances. Hence, the rate at which energy is delivered by a current is the power of the appliance.
- ScienceClass 10CBSE
An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.
Solution: The amount of heat generated can be calculated using the Joule’s law of heating, which is given by the equation H = VIt Substituting the values in the above equation, we get, H = 100 × 5 × 30 = 1.5 × 104 J The amount of heat developed by the electric iron in 30 s is 1.5 × 104 J.
- ScienceClass 10CBSE
Why does the cord of an electric heater not glow while the heating element does?
Solution: The heating element of an electric heater is made of an alloy which has a high resistance. When the current flows through the heating element, the heating element becomes too hot and glows red. The cord is usually made of copper or aluminum which has low resistance. Hence the cord doesn’t glow.
- ScienceClass 10CBSE
What is (a) the highest, (b) the lowest total resistance that can be secured by combinations of four coils of resistance 4 Ω, 8 Ω, 12 Ω, 24 Ω?
Solution: (a) If the four resistors are connected in series, their total resistance will be the sum of their individual resistances and it will be the highest. The total equivalent resistance of the resistors connected in series will be 4 Ω + 8 Ω + 12 Ω + 24 Ω = 48 Ω. (b) If the resistors are connected in parallel, then their equivalent resistances will be the lowest. Their equivalent resistance connected in parallel is
- ScienceClass 10CBSE
What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?
Solution: When the electrical devices are connected in parallel there is no division of voltage among the appliances. The potential difference across the devices is equal to supply voltage. Parallel connection of devices also reduces the effective resistance of the circuit.
- ScienceClass 10CBSE
Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
Solution: The melting point of an alloy is much higher than a pure metal because of its high resistivity. At high temperatures, alloys do not melt readily. Therefore, alloys are used in heating appliances such as electric toasters and electric irons. Use the data in the table given below and answer the following questions. Material Resistiv
- ScienceClass 10CBSE
Let the resistance of an electrical component remain 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?
Solution: The change in the current flowing through the electrical component can be determined by Ohm’s Law. According to Ohm’s Law, the current is given by I = V/R Now, the potential difference is reduced to half keeping the resistance constant, Let the new voltage be V’ = V/2 Let the new resistance be R’ = R and the new amount of current be I’. The change in the current can be determined using Ohm’s
- ScienceClass 10CBSE
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
Solution: Resistance is given by the equation, R = ρ l/A where, ρ is the resistivity of the material of the wire, l is the length of the wire A is the area of the cross-section of the wire. From the equation, it is evident that the area of the cross-section of wire is inversely proportional to the resistance. Therefore, the thinner the wire, the more the resistance and vice versa. Hence, current flows
- ScienceClass 10CBSE
How much energy is given to each coulomb of charge passing through a 6 V battery?
We know that the potential difference between two points is given by the equation, V = W/Q, where, W is the work done in moving the charge from one point to another Q is the charge From the above equation, we can find the energy given to each coulomb as follows: W = V × Q Substituting the values in the equation, we get W = 6V × 1C = 6 J Hence, 6 J of energy is given to each coulomb of charg
- ScienceClass 10CBSE
What is meant by saying that the potential difference between two points is 1 V?
When 1 J of work is done to move a charge of 1 C from one point to another, it is said that the potential difference between two points is 1 V.
- ScienceClass 10CBSE
Name a device that helps to maintain a potential difference across a conductor.
A battery consisting of one or more electric cells is one of the devices that help to maintain a potential difference across a conductor.
- ScienceClass 10CBSE
Calculate the number of electrons constituting one coulomb of charge.
Solution: The value of the charge of an electron is 1.6 × 10-19 C. According to charge quantization, Q = nqe, where n is the number of electrons and qe is the charge of an electron. Substituting the values in the above equation, the number of electrons in a coulomb of charge can be calculated as follows: Therefore, th
- ScienceClass 10CBSE
Define the unit of current.
Solution: The unit of current is ampere. Ampere is defined by the flow of one coulomb of charge per second.
- ScienceClass 10All
what is mcb?
"MCB" can refer to several different things depending on the context. Here are some common meanings: Miniature Circuit Breaker: In electrical engineering, MCB stands for Miniature Circuit Breaker. It is an automatically operated electrical switch designed to protect electrical circuits from damage caused by overcurrent or short circuits. MCBs are commonly used in residential and commercial electrical distribution panels to ensure the safety of electrical system
- ScienceClass 10All
What is an electric cell?
An electric cell, often referred to simply as a cell, is a device that produces electrical energy through chemical reactions. It is a source of direct current (DC) electricity and serves as the fundamental building block of batteries. Electric cells are commonly used to power various electronic devices, ranging from small gadgets like flashlights to larger applications like automobiles. The basic components of an electric cell include: Electrodes: Elect