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Marianna [84]
3 years ago
12

A certain 100W light bulb has an efficiency of 95%. How much thermal energy will this light bulb add to the inside of a room in

2.5h if the bulb is on for the whole time?
Physics
1 answer:
Usimov [2.4K]3 years ago
7 0
Since the bulb consumes 100 watts of power and its efficiency is 95%,
it generates 95 watts of light energy and 5 watts of heat energy whenever
it's turned on.

5 watts means  5 joules of energy per second.

(2.5 hours) x (3,600 seconds/hour) =  9,000 seconds

(9,000 seconds) x (5 joules/second)  =  45,000 joules of heat in 2.5 hours

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A strong lightning bolt transfers an electric charge of about 31 C to Earth (or vice versa). How many electrons are transferred?
olchik [2.2K]

Answer:

m=5.78\times 10^{-3}\ g

n_e=1.935\times 10^{20} is the no. of electrons

Explanation:

Given:

  • quantity of charge transferred, Q=31\ C

<u>No. of electrons in the given amount of charge:</u>

As we have charge on one electron 1.602\times 10^{-19}\ C

so,

n_e=\frac{Q}{e}

n_e=\frac{31}{1.602\times 10^{-19}}

n_e=1.935\times 10^{20} is the no. of electrons

  • Now if each water molecules donates one electron:

Then we require n=1.935\times 10^{20} molecules.

<u>Now the no. of moles in this many molecules:</u>

n_m=\frac{n}{N_A}

where

N_A=6.022\times 10^{23} Avogadro No.

n_m=\frac{1.935\times 10^{20}}{6.022\times 10^{23}}

n_m=3.213\times 10^{-4}\ moles

  • We have molecular mass of water as M=18 g/mol.

<u>So, the mass of water in the obtained moles:</u>

n_m=\frac{m}{M}

where:

m = mass in gram

3.213\times 10^{-4}=\frac{m}{18}

m=5.78\times 10^{-3}\ g

7 0
3 years ago
What is the unit for work is called
emmasim [6.3K]

Answer:

The unit you should use for work done and energy is the joule (J) which is indeed the same as the newton metre (N m).

There is another physical quantity which is the product of force and distance and that is torque or moment of a force.

The unit you should use for torque is the newton metre (Nm) and not the joule.

Naming the units of work done and torque differently helps to emphasis the fact that work done and torque refer to two different physical quantities although the definitions of both quantities have the product of force and distance in them.

work done=force→⋅displacement→ and torque→=force→×displacement→

Hope I helped

4 0
3 years ago
Describe the frequency and wavelength range of radio waves
sammy [17]

Answer:

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. They have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers.

Explanation:

3 0
2 years ago
1. What are the units of : pressure, force , area
White raven [17]

Pressure- Pascal(N/m^2)

Force- Newton

Area-m^2(Square metre)

<u>Explanation:</u>

  • Pressure is force continuous force applied to an object. The applied force is always perpendicular to the surface of the object.
  • Force is a push or pulls on an object by an external body where it changes its state from rest to motion.
  • Force is said to have both magnitude and direction.
  • Area is the portion that shows the scale of a 2D form or configuration in the level. The covering area is its analog on the 2D surface of a 3D object.
6 0
2 years ago
How will unbalanced forces affect the speed and direction of an object
azamat

Answer:

Explanation:

Unbalanced forces will result in the presence of acceleration. The formula

F net = ma

says that if there is a net force present and the object in question has a mass, then an acceleration is present. Now acceleration is constant in this situation because nowhere does it say the acceleration is changing. If acceleration is constant then the velocity is increasing at a steady pace (think linear function!).

The direction of the object depends on the direction that the net force is in. If the net force is to the left, then that object will accelerate to the left.

Hope this helps :)

3 0
3 years ago
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