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4 years ago

An electromagnetic wave has a frequency of and is traveling in a vacuum. The magnetic field is given by ______.

Physics

1 answer:

Reptile [31]4 years ago

4 0

Answer:

c) true. With the magnetic field you can determine the Poynting vector and this is equal to the intensity of the wave

Explanation:

An electromagnetic wave carries energy that is given by the vector of poyntíng

S = 1 / μ₀ E x B

The electric and magnetic fields are related

E = c B

Substituting

S = c /μ₀ B² / 2

The two comes from the average value

Let's examine the claims

a) false to determine the wavelength the frequency is needed

b) False. To find the electric field you need the magnetic field

c) true. With the magnetic field you can determine the Poynting vector and this is equal to the intensity of the wave

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To calibrate the calorimeter electrically, a constant voltage of 3.6 V is applied and a current of 2.6 A flows for a period of 3

hodyreva [135]

Answer : The correct option is, (c) $3.7\times 10^2J/^oC$

Explanation :

First we have to calculate the energy or heat.

Formula used :

$E=V\times I\times t$

where,

E = energy (in joules)

V = voltage (in volt)

I = current (in ampere)

t = time (in seconds)

Now put all the given values in the above formula, we get:

$E=(3.6V)\times (2.6A)\times (350s)$

$E=3276J$

Now we have to calculate the heat capacity of the calorimeter.

Formula used :

$C=\frac{E}{\Delta T}=\frac{E}{T_{final}-T_{initial}}$

where,

C = heat capacity of the calorimeter

$T_{initial}$ = initial temperature = $20.3^oC$

$T_{final}$ = final temperature = $29.1^oC$

Now put all the given values in this formula, we get:

$C=\frac{3276J}{(29.1-20.3)^oC}$

$C=372.27J/^oC=3.7\times 10^2J/^oC$

Therefore, the heat capacity of the calorimeter is, $3.7\times 10^2J/^oC$

7 0

3 years ago

A thermometer initially reading 212F is placed in a room where the temperature is 70F. After 2 minutes the thermometer reads 125

frez [133]

Answer:

91.3°F

Explanation:

Let T be the temperature of the thermometer at any time

T∞ be the temperature of the room = 70°F

T₀ be the initial temperature of the thermometer = 212°F

And m, c, h are all constants from the cooling law relation

From Newton's law of cooling

Rate of Heat loss by the cake = Rate of Heat gain by the environment

- mc (d/dt)(T - T∞) = h (T - T∞)

(d/dt) (T - T∞) = dT/dt (Because T∞ is a constant)

dT/dt = (-h/mc) (T - T∞)

Let (h/mc) be k

dT/(T - T∞) = -kdt

Integrating the left hand side from T₀ to T and the right hand side from 0 to t

In [(T - T∞)/(T₀ - T∞)] = -kt

(T - T∞)/(T₀ - T∞) = e⁻ᵏᵗ

(T - T∞) = (T₀ - T∞)e⁻ᵏᵗ

Inserting the known variables

(T - 70) = (212 - 70)e⁻ᵏᵗ

(T - 70) = 142 e⁻ᵏᵗ

At t = 2 minute, T = 125°F

125 - 70 = 142 e⁻ᵏᵗ

55/142 = e⁻ᵏᵗ

- kt = In (55/142) = In (0.3873)

- k(2) = - 0.9485

k = 0.4742 /min

At time t = 4 mins

kt = 0.4742 × 4 = 1.897

(T - 70) = 142 e⁻ᵏᵗ

e^(-1.897) = 0.15

T - 70 = 142 × 0.15 = 21.3

T = 91.3°F

7 0

3 years ago

Nuclear

luda_lava [24]

Answer:

Energy

Kinetic

Energy in

this

Explanation:

ithikitsthatecauseireallydo

4 0

3 years ago

What is the force on a 1,000-kilogram elevator that is falling under the acceleration of gravity?

rjkz [21]

Answer is in this file

4 0

3 years ago

Read 2 more answers

Why do elements in the same group or column of the periodic table have similar properties? A. They have the same number of proto

Oxana [17]

The Answer is C. The outer shell electrons are the electrons which are involved with chemical reactions and bonding. All elements in the same group have different number of total electrons but ALL have the same number of outer shell electrons. This is why they exhibit similar chemical properties.

3 0

4 years ago