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BabaBlast [244]
3 years ago
12

A ductile metal wire has resistance R. What will be the resistance of this wire in terms of R if it is stretched to three times

its original length, assuming that the density and resistivity of the material do not change when the wire is stretched. (Hint: The amount of metal does not change, so stretching out the wire will affect its cross-sectional area.)
Physics
1 answer:
Ira Lisetskai [31]3 years ago
6 0

Answer:

9R

Explanation:

We know that the resistance is R=\rho *\frac{L}{A}.

If we stretch the wire to a new length L2 = 3L, the cross-sectional area will also change. If the cross-sectional area doesn't change throughout the wire, we can say that:

Volume = L*A = 3L * A2    being A2 the new area after stretching the wire.

Since the volume remains the same we conclude that A2 = A/3

With this information, we calculate the new resistance:

R2=\rho *\frac{L2}{A2}=\rho *\frac{3*L}{A/3}=\rho * 9 * \frac{L}{A}

Since R=\rho *\frac{L}{A}, and by simple inspection of the previous equation, we get:

<em>R2 = 9*R</em>

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For when white light is passed through a diffraction grating, the color closest to the center bright spot corresponds toa. Yello
gizmo_the_mogwai [7]

Answer:

Option e. Blue/Violet

Explanation:

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Red light has the longest wavelength and is least scattered whereas Violet light with the shortest wavelength is the one to get most scattered and as we move far from bright spot at the center, there is an increase in the wavelength of light, thus the color that corresponds to the closest one is Violet with the shortest wavelength in the band.

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Suppose a ray of light traveling in a material with an index of refraction n a reaches an interface with a material having an in
KATRIN_1 [288]

Answer: C and D

Explanation: One of the first rule for total internal reflection to occur is that the ray must move from a dense to a less dense medium, hence refractive index of medium a must be greater than that of b.

When a ray moves from a dense to a less dense medium, the refracted ray moves away from the normal thus increasing the size of the angle of refraction (total internal refraction occurs when the angle of refraction is 90° and the angle of incidence at this point is known as the critical angle), hence the angle of incidence must be greater than the critical angle.

These points verifies option C and D

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3 years ago
A balloon-powered car rolls across the floor at a speed of 0.711 m/s. How long does it take to cover 8.25 m?
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Answer:

Time = 11.60 seconds.

Explanation:

Speed can be defined as distance covered per unit time. Speed is a scalar quantity and as such it has magnitude but no direction.

Mathematically, speed is given by the equation;

Speed = \frac{distance}{time}

Given the following data;

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To find the time;

Making time the subject of formula, we have;

Time = \frac{distance}{speed}

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Time = \frac{8.25}{0.711}

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