Electricity
- Explain the following. (a) Why is the tungsten used almost exclusively for filament of electric lamps? a) The melting point and of Tungsten is an alloy which has very high melting point and very high resistivity so does not burn easily at a hi... 2
- An electric heater of resistance 8 Ω draws 15 A from the service mains 2 hours. Calculate the rate at which heat is Rate of heat produced by a device is given by the expression for power as, P= I²R Where, Resistance of the electric heater, R= 8 Ω Current d... 1
- Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes? Energy consumed by an electrical appliance is given by the expression,H= Pt Where, Power of the appliance = P Time = t Energy consumed by a... 1
- Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. Both the bulbs are connected in parallel. Therefore, potential difference across each of them will be 220 V, because no division of voltage... 1
- Compare the power used in the 2 Ω resistor in each of the following circuits: (i) a 6 V battery in series with 1 Ω and 2 (i) Potential difference, V = 6 V 1 Ω and 2 Ω resistors are connected in series. Therefore, equivalent resistance of the circuit, R = 1 + 2... 1
- A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance https://www.youtube.com/watch?v=Ru4TReFRK7A&ab_channel=Darshanclasses 2
- Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can Resistance R₁ of the bulb is given by the expression, Supply voltage, V = 220 V Maximum allowable current, I = 5 A Rating of an electric bul... 2
- Show how you would connect three resistors, each of resistance 6 Ω, so that the combination has a resistance of https://youtu.be/LggubtJYvrU 2
- How many 176 Ω resistors (in parallel) are required to carry 5 A on a 220 V line? For x number of resistors of resistance 176 Ω, the equivalent resistance of the resistors connected in parallel is given by Ohm's law asV= I... 1
- 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, respectively There is no current division occurring in a series circuit. Current flow through the component is the same, given by Ohm’s law as V= IR I= V... 1
- When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Resistance (R) of a resistor is given by Ohm's law as,V= IR R= V/I Where, Potential difference, V= 12 V Current in the circuit, I= 2.5 mA =... 1
- A copper wire has diameter 0.5 mm and resistivity of 1.6 × 10−8 Ω m. What will be the length of this wire to make https://youtu.be/gdC4O4SbCAg 2
- How is a voltmeter connected in the circuit to measure the potential difference between two points? To measure the potential difference between two points, a voltmeter should be connected in parallel to the points. 1
- Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and Correct option is c) 1:4 2
- 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 Correct option is d) 25 W 2
- Which of the following terms does not represent electrical power in a circuit? (a) I2R (b) IR2 (c) VI (d) V2/R Correct option is b) IR² 2
- A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. Correct option is d) 25 2
- An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h. Power (P) is given by the expression,P = VI Where, Voltage,V = 220 V Current, I = 5 A P= 220 x 5 = 1100 W Energy consumed by the motor = Pt... 1
- What determines the rate at which energy is delivered by a current? The rate of consumption of electric energy in an electric appliance is called electric power. Hence, the rate at which energy is delivered b... 1
- An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s The amount of heat (H) produced is given by the joule's law of heating asH= Vlt Where, Current, I = 5 A Time, t = 30 s Voltage, V = Current... 1
- Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50 V Given Charge, Q = 96000C Time, t= 1hr = 60 x 60= 3600s Potential difference, V= 50volts Now we know that H= VIt So we have to calculate I fi... 1
- Why does the cord of an electric heater not glow while the heating element does? The heating element of the heater is made up of alloy which has very high resistance so when current flows through the heating element, it b... 1
- What is (a) the highest, (b) the lowest total resistance that can be secured by combinations of four coils of resistance There are four coils of resistances 4 Ω, 8 Ω, 12 Ω and 24 Ω respectively. (a) If these coils are connected in series, then the equivalent re... 1
- How can three resistors of resistances 2 Ω, 3 Ω and 6 Ω be connected to give a total resistance of (a) 4 Ω, (b) 1 Ω? https://youtu.be/4fV86enlX04 2