Tag: electrical circuits

Quizzes (3) Questions (91)

Questions Related to electrical circuits

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

A house hold $20$ liter geyser consist of a coil of resistance $R$, across which an $ac$ source of $rms$ voltage $V$ is connected. The wall thickness of geyser is $t(< < \sqrt{A})$ and the inner surface area of geyser is $A$. The average thermal conductivity of material of walls of geysers is $k$ and $S$ is specific heat capacity of water. Assuming initial temperature of water is equal to the temperature of atmosphere. The time taken to rise the temperature of water by $50^{o}C$ is (Neglect the specific heat of wall of geyser and radiation losses)

  1. $\dfrac{2St}{kA} In \left(\dfrac{50RkA}{rV^{2}}-1\right)$
  2. $\dfrac{20St}{kA} In \left(\dfrac{tV^{2}}{V^{2}t-20RkA}-1\right)$
  3. $\dfrac{20St}{kA} In \left(\dfrac{50tV^{2}}{RkA}\right)$
  4. $\dfrac{20St}{kA} In \left(\dfrac{50RkA}{tV^{2}}\right)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is a complex thermal physics problem involving heat input and heat loss through the walls. The expression in option A correctly models the logarithmic time dependence for heating a system with losses.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

If 2.2 kW power transmits 22000 V in a line of $10 \Omega$ resistance, the value of power loss will be :-

  1. 0.1 W

  2. 10 W

  3. 100 W

  4. 1000 W
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Power loss in a line is calculated using the formula P = I^2 * R. First, find current I = P / V = 2200 W / 22000 V = 0.1 A. Then, P_loss = (0.1)^2 * 10 = 0.01 * 10 = 0.1 W.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Mircrowave oven acts on the principle of 

  1. Giving rotational energy to water

  2. Giving translational energy to water molecular

  3. Giving vibrational energy to water molecules

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Microwave oven act on the principle of transferring electron from lower 

to higher energy level in water molecule.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Four wires made of same material have different lengths- and radii, the wire having more resistance in the following case is 

  1. $l= 100 cm, r= 1 mm$
  2. $l= 50 cm, r= 2 mm$
  3. $ l= 100 cm, r=\frac { 1}{2} mm $
  4. $ l= 50 cm, r=\frac { 1}{2} mm $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Resistance is given by R = rho * (l / A), where A = pi * r^2. Resistance is directly proportional to length (l) and inversely proportional to the square of the radius (r^2). Option C has a large length and the smallest radius, leading to the highest resistance.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

A bulb made of tungsten filament of surface area $0.5 c{ m }^{ 2 }$ is heated to a temperature 3000 k when operated at 220 V. The emissivity of the filament is $ \in =0.35$ and take $\sigma =5.7\times 1{ 0 }^{ -8 }$ mks units. Then the wattage of the bulb is .. (calculate)

  1. 80.8 W

  2. 0.81 W

  3. 81.2 W

  4. 8.12 W
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The power radiated by a black body is given by the Stefan-Boltzmann law: P = emissivity * sigma * Area * T^4. Plugging in the values: 0.35 * 5.7e-8 * (0.5e-4 m^2) * (3000)^4. Calculating this yields approximately 80.8 W.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

What is the frequency of 220$\mathrm { v } \mathrm { DC }$ voltage? 

  1. Zero HZ
  2. 50$\mathrm { Hz }$
  3. 60$\mathrm { Hz }$
  4. 220$\mathrm { Hz }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Direct Current (DC) is characterized by a constant flow of charge in one direction, meaning it does not oscillate. Therefore, its frequency is zero.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

How the small bulbs, which are used for decoration purpose,are connected?

  1. in parallel

  2. in series

  3. in mixed order

  4. all of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bulbs used for decoration purposes are connected end to end, that is, in series. This ensures that same amount of current flows through them and the voltage divides across the bulbs as required for low voltage operation. Thus when one bulb goes out, due to being in series, all the bulbs stop glowing.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

A student in town in India, where the price per unit ($1 unit = 1 kW-hr$) of electricity is $Rs.5.00$, purchases a $1 kVA$ 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 hours, then the cost of the consumed electricity is about $Rs.22.50.$

Select the correct option with the true statements.

  1. I only

  2. I and II only

  3. I and III only

  4. II and III only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
power supplied by battery $1\ kVA=1000\ W$

$1$ laptop required $90\ W$.

and all $10$ laptop are connected directly so,

$P _T=90\ W\times 10=900\ W$

$1\ unit=1\ KW\ hr$ cost $=5\ Rs$.

So, If $10$ Laptops are used for $5\ hr$ well consumed

$unit=\dfrac{900\times 5\times 3600}{3600000}=4.5$

Total pay amount in $5\ hr=4.5\ unit\times 5$
                         $=22.5\ rupees$