EASY
Earn 100

Assertion: Fuse wire of any electronic equipment must have high resistance and low melting point.
Reason: Fuse is used for small current flow only.

50% studentsanswered this correctly

Important Questions on Current Electricity

MEDIUM
A current of 2mA was passed through an unknown resistor which dissipated a power of 4.4 W. Dissipated power when an ideal power supply of 11V is connected across it is:
HARD
The resistance of an electrical toaster has a temperature dependence given by RT=R01+αT-T0 in its range of operation. At T0=300 K, R=100 Ω and at T=500 K, R=120 Ω. The toaster is connected to a voltage source at 200 V and its temperature is raised at a constant rate from 300 to 500 K in 30 s. The total work done in raising the temperature is :

Note: This question was awarded as the bonus since all options were incorrect in the exam. 
MEDIUM
A cell of internal resistance r drives current through an external resistance R. The power delivered by the cell to the external resistance will be maximum when:
EASY
The charge flowing through a resistance R varies with time t as Q=at-bt2 where a and b are positive constants. The total heat produced in R is:
EASY
If the current through a resistor in a circuit increases by 3%, the power dissipated by the resistor
MEDIUM
In a building there are 15 bulbs of 45W , 15 bulbs of 100W,15 small fans of 10W and 2 heaters of 1kW . The voltage of electric main supply is 220V . The minimum fuse capacity (rated value) of the building will be:
EASY
In which of the following devices, the eddy current effect is not used?
HARD
A student in a town in India, where the price per unit (1 unit =1kWh ) of electricity is  5.00, purchases a 1kVA UPS (uninterrupted power supply) battery. A day before the exam, 10 friends arrive to the student's home with their laptops and all connect their laptops to the UPS. Assume that each laptop has a constant power requirement of 90 W. Consider the following statements.
I. All the 10 laptops can be powered by the UPS, if connected directly.
II. All the 10 laptops can be powered, if connected using an extension box with a 3 A fuse.
III. If all the 10 friends use the laptop for 5 h, then the cost of the consumed electricity is about  22.50 .
Select the correct option with the true statements.
HARD

A light bulb of resistance R=16 Ω is attached in series with an infinite resistor network with identical resistances as shown below. A 10 V battery derives a current in the circuit. What should be the value of r such that the bulb dissipates about 1 W of power?

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MEDIUM

A uniform metallic wire of length L is mounted in two configurations. In configuration 1 (triangle), it is an equilateral triangle and a voltage, V is applied to corners A and B. In configuration 2 (circle), it is bent in the form of a circle, and the potential V is applied at diametrically opposite points P and Q. The ratio of the power dissipated is configuration 1 to configuration 2 is.

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HARD

In the circuit shown, the heat produced in 5 Ω resistor is 10 cal s-1. The heat produced per sec in 4 Ω resistor will be

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HARD
The supply voltage to a room is 120 V. The resistance of the lead wires is 6  Ω . A 60 W bulb is already switched on. What is the decrease of voltage across the bulb, when a 240 W heater is switched on in parallel to the bulb?
EASY

ADC source with internal resistance R0 is connected to circuit as shown in the figure. The value of R for which the power generated in the circuit is the maximum is

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MEDIUM
The resistive network shown below is connected to a D.C. source of 16 V. The power consumed by the network is 4 W. The value of R is:
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MEDIUM

Consider the following two circuits

A : 20 bulbs are connected in series to a power supply line

B : 20 bulbs identical to A are connected in a parallel circuit to an identical power supply line

Identify which of the following is not true

EASY
Two identical cells are first connected in series and then in parallel. The ratio of power consumed by them is
EASY
An inverter battery operated on 24 V and has negligible internal resistance. It is rated at 140 ampere-hour. What external resistance would have to be connected to the battery, if it were to be discharged in 14 hours.
HARD
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In the circuit shown, the resistance r is a variable resistance. If for r=fR , the heat generation in r is maximum then the value of f is
MEDIUM
A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance, R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is
MEDIUM
Two electric bulbs, rated at 25 W, 220 V  and 100 W, 220 V, are connected in series across a 220 V voltage source. If the 25 W and 100 W bulbs draw powers P1 and P2 respectively, then: