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current electricity | basic questions | class 12 physics | advguruji | Physics Advocate

Q1.
An electron beam has an aperture of 2 mm². A total of 7 × 10¹⁵ electrons flow through any perpendicular cross-section per second. Calculate the current density of the electron beam.

Q2.
The charge in a given wire varies with time, given by -
    q = 3t³ - t²
Where, q in 'C' and t in 'secs'.
Find the current flowing in the wire at 4th second.

Q3.
The current flowing in a conductor is the function of time, given by -
   I = 8t - 3
Where, I in 'Ampere' and t in'secs'.

Find the total charge flowed in first 5 seconds in the conductor.
Also, find the charge which flowed from 6th to 8th second.

Q4. A storage battery of EMF 8 volt and internal resistance 0.5 ohm is being charged by a 120 volt dc supply using a series resistor of 15.5 ohm. What is the terminal voltage of the battery during charging? What is the purpose of having a series resistor in the charging circuit?

Q5. The manufacturer sticker on an electric bulb reads 220 V, 60 W. If the supply voltage available is 100 V then what current will be drawn by the bulb?

Q6. Find the percentage increase or decrease in the resistance of a metallic wire at 24°C if it is stretched to 130% of its original length.

Q7. Two conducting wires X and Y of same diameter across a battery. If the number density of electrons in X is twice that in Y, find the ratio of drift velocity of electrons in the two wires if both wires carry the same current.


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           ANSWERS

A1.
560 Am-²

A2.
136 A

A3.
85 C, 106 C

A6. 69% increase in Resistance

Introduction to CURRENT ELECTRICITY (Basic Concepts)

by  www.advguruji.blogspot.com
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