Work and Energy Test

Result

Work and Energy Test - 39

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
1 / -0

A lamp rated $$20W$$ and an electric iron rated $$50W$$ are used for $$2$$ hour everyday. Calculate the total energy consumed in $$20 $$ days.

A
$$14kwh$$

B
$$2.8kwh$$

C
$$40kwh$$

D
None of these

Solution

Energy consumed by lamp in 2 hour $$E_l = 0.02\times 2 = 0.04$$ kWh per day
Energy consumed by iron in 2 hour $$E_i = 0.05\times 2 = 0.1$$ kWh per day
$$\therefore$$ Total energy consumed by both appliance in $$20$$ days,
$$E_T = (E_l+E_i)\times 20 = (0.04+0.1)\times 20 = 2.8$$ kWh
Question 2
1 / -0

Number of KWh in 1 Joule.

A
$$\displaystyle 3.6\times { 10 }^{ 6 }\ KWh$$

B
$$\displaystyle 2.77\times { 10 }^{ -7 }\ KWh$$

C
$$\displaystyle 600\ KWh$$

D
$$\displaystyle 1.6\times { 10 }^{ -19 }\ KWh$$

Solution

We know that $$KWh$$ is kilo watt-hour-
In SI unit-
$$K = 10^3$$
$$hour = 3600\ s$$
$$1\ kWh = 3.6\times 10^6\ J$$
$$\therefore$$ $$1$$ $$J = \dfrac{1}{3.6\times 10^6} = 2.77\times 10^{-7}$$ $$kWh$$
Question 3
1 / -0

Which of these units of energy is the largest?

A
$$1\ Calorie$$

B
$$1\ Joule$$

C
$$1\ Erg$$

D
$$1\ Kilowatt-hour$$

Solution

Energy is the ability to do work.
$$1\ {calorie} = 4.186\ J$$
$$1\ erg= 1\times 10^{-7}\ J$$
$$1\ kWh=3.6\times 10^{6}$$ $$J$$
$$1\ kilowatt-hour$$ is the largest unit of energy.
Question 4
1 / -0

In which form, the energy is stored in a fuel?

A
Potential energy

B
Thermal energy

C
Kinetic energy

D
Chemical energy

Solution

Chemical energy is energy stored in the bonds of atoms and molecules. Batteries, biomass, petroleum, natural gas, and coal are examples of chemical energy. Chemical energy is converted to thermal energy when people burn wood in a fireplace or burn gasoline in a car's engine.
Question 5
1 / -0

Which one of the following energies cannot be possessed by a body at rest?

A
Potential energy

B
Kinetic energy

C
Thermal energy

D
Magnetic energy

Solution

Kinetic energy is possessed by a body by virtue of its state of motion. So, a body at rest cannot possess kinetic energy. A body at rest will possess potential energy. Thermal and magnetic energies are irrespective of state of rest or of motion of a body.
Question 6
1 / -0

A freely falling object eventually stops on reaching ground. What happens to its potential and kinetic energy while falling?

A
Potential energy decreases and Kinetic energy increases

B
Potential energy increases and Kinetic energy increases

C
Potential energy increases and Kinetic energy decreases

D
None

Solution

When an object release from a certain height then it starts to move toward the earth. During its motion, work is done by gravity along the direction of motion. Hence kinetic energy of the object started to increase.
Also, Potential energy is a function of height, so when the height of an object decreases, its potential also decreases.
Hence Option A.
Question 7
1 / -0

What is practical unit of power?

A
Watt

B
Kilo watt

C
Horse power

D
None of these

Solution

Practical unit of power is horse power $$\left(hp\right)$$.
$$1\ hp = 746 W$$ , where $$W$$ is Watt (the SI unit of power).
Question 8
1 / -0

A certain household has consumed $$250$$ units of energy during a month. How much energy is this in joules?

A
$$9 \times 10^{10}\ J$$

B
$$9 \times 10^{8}\ J$$

C
$$9 \times 10^{9}\ J$$

D
$$9 \times 10^{-8}\ J$$

Solution

Hint: Conversion of KWh to joule.

Step 1: Commercial unit of energy is KWh.

   $$1\; KWh = 10^3\; W = 10^3\; JS^{-1}$$

  $$1\;hr = 60\times60 = 3600\;sec$$

Therefore, $$1\;KWh = 1\; KW \times1\;hr$$
$$=10^3 \times 3600$$
$$=3.6 \times 10^6 \;J$$

Step 2: Calculation according to question

Energy consumption $$=250\;KWh$$
$$= 250\times3.6\times10^6\;J$$
$$=900\times10^6\;J$$
$$=9\times10^8\;J$$ or $$900\;MJ$$

Hence, Option (B) is correct.
Question 9
1 / -0

Find energy in kWh consumed in 10 hours by four devices of power $$500\ W$$ each?

A
$$10\ kWh$$

B
$$20\ kWh$$

C
$$30\ kWh$$

D
$$40\ kWh$$

Solution

Hint:
Power is the ratio of the work and the time. Energy consumed in four devices is four times the energy consumed in one device.

Step 1: Given data
Power consumed by each device, $$P=500\ W=0.50\ kW$$
Time, $$t=10\ h$$
Expression for the energy consumed is written as,
$$W=P\times t$$

Step 2: Calculations,
Energy consumed by each device, $$W=0.50 \times 10 = 5kWh$$
Energy consumed by four devices, $$ = 4 \times 5 = 20\ kWh$$
Question 10
1 / -0

Smallest commercial unit of energy is

A
Kilowatt hour

B
Watt second

C
Watt hour

D
Watt minutes

Solution

Smallest commercial unit of energy is called Watt hour $$(Wh)$$. One watt hour is the energy consumed when $$1 \ watt$$ of power is used for $$1 \ hour.$$

User

Question Analysis

Correct -
Wrong -
Skipped -

My Perfomance

Score
-
out of -
Rank
-
out of -

Re-Attempt Weekly Quiz Competition

Work and Energy Test - 39

Result

Work and Energy Test - 39

Score

-

Rank

-

SHARING IS CARING

Question 1

$$14kwh$$

$$2.8kwh$$

$$40kwh$$

None of these

Solution

Question 2

$$\displaystyle 3.6\times { 10 }^{ 6 }\ KWh$$

$$\displaystyle 2.77\times { 10 }^{ -7 }\ KWh$$

$$\displaystyle 600\ KWh$$

$$\displaystyle 1.6\times { 10 }^{ -19 }\ KWh$$

Solution

Question 3

$$1\ Calorie$$

$$1\ Joule$$

$$1\ Erg$$

$$1\ Kilowatt-hour$$

Solution

Question 4

Potential energy

Thermal energy

Kinetic energy

Chemical energy

Solution

Question 5

Potential energy

Kinetic energy

Thermal energy

Magnetic energy

Solution

Question 6

Potential energy decreases and Kinetic energy increases

Potential energy increases and Kinetic energy increases

Potential energy increases and Kinetic energy decreases

None

Solution

Question 7

Watt

Kilo watt

Horse power

None of these

Solution

Question 8

$$9 \times 10^{10}\ J$$

$$9 \times 10^{8}\ J$$

$$9 \times 10^{9}\ J$$

$$9 \times 10^{-8}\ J$$

Solution

Question 9

$$10\ kWh$$

$$20\ kWh$$

$$30\ kWh$$

$$40\ kWh$$

Solution

Question 10

Kilowatt hour

Watt second

Watt hour

Watt minutes

Solution

User

Question Analysis

My Perfomance

Score

-

Rank

-

Results Announcement on: coming Monday

Stay Tuned: We’ll update you on your result via email or SMS.