Physics - Current Electricity Question with Solution | TestHub

PhysicsCurrent ElectricityElectrical PowerEasy2 minPYQ_2020

PhysicsEasysingle choice

A $30 V, 90 W$ lamp is to be operated on a $120 V$ DC line. For proper glow, a resistor of $Ω$ should be connected in series with the lamp.

Options:

Answer:

Solution:

Resistance of the lamp,
$R_{0} = \frac{V^{2}}{P} = \frac{{(30)}^{2}}{90} = 10 Ω$

Current in the lamp,
$i = \frac{30}{10} = 3 A$

When lamp is operated on a $120 V$ , then resistance,
$R^{'} = \frac{V^{'}}{i} = \frac{120}{3} = 40 Ω$

Thus, for proper glow, the resistance required to the put in series will be
$R = R^{'} - R_{0} = 40 - 10 = 30 Ω$

Stream:NTA_ABHYAS_NEETSubject:PhysicsTopic:Current ElectricitySubtopic:Electrical Power

⏱ 2mℹ️ Source: PYQ_2020

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