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प्रश्न
- What is meant by electric current?
- Name and define its unit.
- Which instrument is used to measure the electric current? How should it be connected in a circuit?
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उत्तर
- (i) Electric current is often termed as .current. and it is represented by the symbol .I. It is defined as the rate of flow of charges in a conductor.
(ii) The electric current represents the amount of charges flowing in any cross section of a conductor (say a metal wire) in unit time. - The SI unit of electric vurrent is ampere (A) The current flowing through a conductor is said to be one ampere, when a charge of one coulomb flows across any cross - section of a conductor in one second.
Hence,
1 ampere = `"1 coulomb"/"1 second" ` - (i) Ammeter is used to measure the current.
(ii) An Ammeter is connected in series with circuit.
(iii) The Ammeter is a low impedance device connecting it in parallel with the circuit would cause a short circuit, damaging the Ammeter or the circuit.
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संबंधित प्रश्न
Two lamps, one rated 40 W at 220 V and the other 60 W at 220 V, are connected in parallel to the electric supply at 220 V.
(a) Draw a circuit diagram to show the connections.
(b) Calculate the current drawn from the electric supply.
(c) Calculate the total energy consumed by the two lamps together when they operate for one hour.
Two resistors of 2.0 Ω and 3.0 Ω are connected (a) in series (b) in parallel, with a battery of 6.0 V and negligible internal resistance. For each case draw a circuit diagram and calculate the current through the battery.
The following table shows the current in Amperes and potential differences in Volts.
- Find the average resistance.
- What will be the nature of the graph between the current and potential difference? (Do not draw a graph.)
- Which law will the graph prove? Explain the law.
| V (volts) | I (amp) |
| 4 | 9 |
| 5 | 11.25 |
| 6 | 13.5 |
Fig . shows the core of a transformer and i ts input and output connections
State the material used for the core and describe th e structure of the core.
(a) Use the values given in the diagram to calculate the turns ratio for the transformer and connections, labeling all parts of the diagram .
(b) If a current of 2 A is taken from th e output, calculate th e current in the input circuit (Assume the transformer to be ideal ).
Match the items in column-I to the items in column-II:
| Column - I | Column - II |
| (i) electric current | (a) volt |
| (ii) potential difference | (b) ohm meter |
| (iii) specific resistance | (c) watt |
| (iv) Electrical power | (d) joule |
| (v) electrical energy | (e) ampere |
What happens when the switch in a circuit is turned OFF (open circuit)?
