Please select a subject first
Advertisements
Advertisements
Two resistors A and B of resistance 4 Ω and 6 Ω respectively are connected in parallel. The combination is connected across a 6 volt battery of negligible resistance. Calculate: (i) the power supplied by the battery, (ii) the power dissipated in each resistor.
Concept: undefined >> undefined
A battery of e.m.f 15 V and internal resistance 2 Ω is connected to two resistors of resistance 4 ohm and 6 ohm joined in series. Find the electrical energy spent per minute in 6 ohm resistor.
Concept: undefined >> undefined
Advertisements
Water in an electric kettle connected to a 220 V supply took 5 minutes to reach its boiling point. How long would it have taken if the supply voltage had fallen to 200 V?
Concept: undefined >> undefined
An electric toaster draws 8 A current in a 220 V circuit. It is used for 2 h. Find the cost of
operating the toaster if the cost of electrical energy is Rs. 4.50 per kWh.
Concept: undefined >> undefined
An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at Rs. 5.40 per unit.
Concept: undefined >> undefined
A geyser is rated 1500 W, 250 V. This geyer is connected to 250 V mains. Calculate:
(i) the current drawn
(ii) the energy consumed in 50 hours, and
(iii) the cost of energy consumed at Rs. 4.20 per kWh
Concept: undefined >> undefined
You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper wire and a switch. (a) Draw a circuit diagram to represent the process. (b) label the poles of the electromagnet.
Concept: undefined >> undefined
The adjacent diagram shows a coil would around a soft iron bar XY. (a) State the polarity at the end X and Y as the switch is pressed. (b) Suggest one way increasing the strength of electromagnet so formed.
Concept: undefined >> undefined
State two ways through which the strength of an electromagnet can be increased.
Concept: undefined >> undefined
Complete the following sentence :
……… energy is converted into …………energy by an electric motor.
Concept: undefined >> undefined
State two factors on which the magnitude of induced e.m.f. depend.
Concept: undefined >> undefined
Explain why an induced current must flow in such a direction so as to oppose the change producing it.
Concept: undefined >> undefined
Explain the significance of Lenz’s law to show the conservation of energy in electromagnetic induction.
Concept: undefined >> undefined
The following diagram in Fig.10.42 shows a coil of several turns of copper wire connected to a sensitive centre zero galvanometer G near a magnet NS. The coil is free to move in the direction shown in the diagram.
(i) Describe the observation if the coil is rapidly moved.
(ii) How would the observation be altered if (a) the coil has twice as many turns (b the coil was made to move three times as fast?
Concept: undefined >> undefined
The following diagram in Fig. 10.44 shows a coil X connected to a sensitive centre –zero galvanometer G and a coil P connected to a battery through a switch S.
(a) Describe the observation when the switch S is (i) closed suddenly, (ii) then kept closed, (iii) finally opened.
(b) Name and state the law which explains the above observations.
Concept: undefined >> undefined
For what purpose are the transformers used? Can they be used with a direct current source?
Concept: undefined >> undefined
How are the e.m.f in the primary and secondary coils of a transformer related with the number of turns in these coils?
Concept: undefined >> undefined
The secondary windings of a transformer in which the voltage is stepped down are usually made of thicker wire than the primary. Explain why.
Concept: undefined >> undefined
Why is the iron core of a transformer made laminated (thin sheets) instead of being in one solid piece?
Concept: undefined >> undefined
