MEDIUM
JEE Main/Advance
IMPORTANT
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A micro-ammeter has a resistance of 100 Ω and full scale range of 50 μA. It can be used as a voltmeter and an ammeter of a higher range provided a resistance is added to it. Pick the correct range and resistance combination (s).

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Important Questions on Current Electricity

MEDIUM
JEE Main/Advance
IMPORTANT

Two cells of unequal emfs ε1 and ε2 and internal resistances r1 and r2 are joined as shown. VA and VB are the potentials at A and B, respectively. 

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EASY
JEE Main/Advance
IMPORTANT

In the potentiometer arrangement shown, the driving cell D has emf ε and internal resistance r. The cell C, whose emf is to be measured, has emf ε2 and internal resistance 2r. The potentiometer wire is the potentiometer wire is 100-cm long. If balance is obtained at the length AJ=l.

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EASY
JEE Main/Advance
IMPORTANT
Choose the correct alternatives.
HARD
JEE Main/Advance
IMPORTANT

In the circuit shown below, the key is pressed at time t= 0. Which of the following statement(s) is (are) true?

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MEDIUM
JEE Main/Advance
IMPORTANT
Let C be the capacitance of a capacitor discharging through a resistor R. Suppose t1 is the time taken for the energy stored in the capacitor to reduce to half its initial value and t2 is the time taken for the charge to reduce to one-fourth its initial value. Then the ratio t1/t2 will be
MEDIUM
JEE Main/Advance
IMPORTANT
A resistor R and 2 μF capacitor in series are connected through a switch to 200 V direct supply. Across the capacitor is a neon bulb that lights up at 120 V. Calculate the value of R to make the bulb light up 5 s after the switch has been closed. log102.5=0.4
EASY
JEE Main/Advance
IMPORTANT
A combination of two identical capacitors, a resistor R and a DC voltage source of voltage 6 V is used in an experiment on a CR circuit. It is found that for a parallel combination of the capacitor the time in which the voltage of the fully charged combination reduces to half its original voltage is 10 second. For series combination, the time needed for reducing the voltage of the fully charged series combination by half is
MEDIUM
JEE Main/Advance
IMPORTANT

The figure shows an experimental plot discharging of a capacitor in an RC circuit. The time constant τ of this circuit lies between

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