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Ede4ka [16]
3 years ago
10

Consider two copper wires. One has twice the length and twice the cross-sectional area of the other. How do the resistances of t

hese two wires compare? A) Both wires have the same resistance. B) The shorter wire has twice the resistance of the longer wire. The longer wire has twice the resistance of the shorter wire. D) The longer wire has four times the resistance of the shorter wire. E) The shorter wire has four times the resistance of the longer wire.
Physics
1 answer:
Makovka662 [10]3 years ago
7 0

Answer:

option (a)

Explanation:

Wire 1:

length = 2L

Area = 2 A

Wire 2: length = L

Area = A

As we know that the resistance of a wire is directly proportional to the length of the wire and inversely proportional to the area of crossection of the wire.

Let ρ be the resistivity of the cooper wire.

Resistance of wire 1

R1 = ρ x 2L / 2 A = ρ L / A

Resistance of wire 2:

R2 = ρ x L /  A = ρ L / A

As R1 = R2

It means both the wires have same resistance.

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What is the weight of an object (mass = 60 kilograms) on Mars, where the acceleration due to gravity is 3.75 meters/second2?
enot [183]

Answer:

Weight of an object = 225 newtons

Explanation:

Given:

Mass = 60 kilograms

Acceleration due to gravity = 3.75 m/s²

Find:

Weight of an object

Computation:

Weight of an object = Mass x Acceleration due to gravity

Weight of an object = 60 x 3.75

Weight of an object = 225 newtons

5 0
3 years ago
please help !!!!!!!!!!!!!!!!!! give the answer to the question i. which lighthouse will be warmer during the day time and why ?
Lostsunrise [7]

Answer:

I. light house 1 will be warmer during the day ii. light house 2 will be warmer at night.

Explanation:

Because the land conducts heat better than water the light house farthest away from the water will get hotter during as the ground will heat up faster than the water. But this also means that the ground will lose heat faster at night where the water won't making the light house closest to the water hotter at night.

4 0
3 years ago
What does H-R diagram stand for?
Nina [5.8K]
Hertzsprung-Russell <span>Diagram</span>
4 0
3 years ago
Read 2 more answers
Which scientist was the first to conclude through experimentation that atoms have positive charges in their nuclei?
Pavel [41]
<h2>Answer: Ernest Rutherford </h2>

Ernest Rutherford was a British physicist and chemist of New Zealand origin, who conducted a series of experiments together with Hans Geiger and Ernest Marsden; where the result led him to propose a new atomic model.

It should be noted that at that time, the "accepted" atomic model was Thomson's raisin pudding atomic model<u> </u><em><u>(electrons with negative charge immersed an the atom of positive charge that counteracted the negative charge of the electrons, like raisings embedded in a pudding)</u></em>, who discovered the electron and formerly was a professor of Rutherford.  

Now, the experiment conducted under the direction of Ruherford at the laboratories of the University of Manchester during the year 1911; was for the purpose of <u>corroborating Thomson's atomic model</u>. To achieve this, a thin metal sheet was bombarded with alpha particles (nuclei of helium gas).

The idea was that these alpha particles, having positive electric charge, were attracted by the atom's negative charges and repelled by the positive charges, and it was expected that they would pass through the thin sheet without hardly deviating. Then, to observe the crash site of the particle, a phosphorescent screen was placed behind and on the sides of the metal sheet.

For according to Thomson's atomic model the positive and negative charges were evenly distributed, the sphere (the atom) had to be electrically neutral, and <u>the alpha particles would pass through the sheet without deviating. </u>

However, the results were surprising:

As expected, most of the particles went through the sheet without deviating.

<h2>But some suffered large deviations and, most importantly, <u>a small number of particles bounced backwards</u>. </h2>

That is:

<h2>The alpha particle beam was scattered (repelled) when it hit the thin metal sheet. </h2>

These facts could not be explained by Thomson's atomic model, so Rutherford developed another, suggesting that:

<h2><em>There is a concentration of charge in the center of the atom (which was later called nucleus) surrounded by electrons. </em></h2>

This new model could explain the proven fact in his experiments that some particles bounced in the direction opposite to the incident particles, because the electrical charge of this nucleus was positive, equal to the electrical charge of the alpha particles.

This is how Rutherford proposed a new atomic model and discovered the existence of the nucleus. However, this was not the definitive model, because on 1913 it was replaced by Bohr's.

8 0
3 years ago
A current of 5 A exists in a copper wire of length 50 m and diameter of 2.5 mm when applying a
taurus [48]

Answer:

a) 1273.23 A/m^2

b) 7.19*10^-5 m/s

c) 236881.7 Ohms

Explanation:

(a) To find the current density you use the following formula:

J=\frac{I}{A}=\frac{I}{\pi r^2}

I: current in the wire

A: cross area of the wire

r: radius of the wire

J=\frac{5A}{\pi(1.25*10^{-3}m)^2}=1273.23\frac{A}{m^2}

(b) The electron drift speed is given by:

v_d=\frac{I}{nqA}=\frac{I}{nq\pi r^2}

n: number of conduction electrons per m^3

q: charge of the electron = 1.6*10^-19C

The number of free electrons is calculated by using:

n=\frac{\rho N_A}{M}\\\\n=\frac{(9*10^{3}kg/m^3)(6.22*10^{23})}{63.54*10^{-3}}=8.5*10^{28}

Next, you replace the values of the parameters in the equation for vd:

v_d=\frac{5A}{(8.85*10^{28}m^{-3})(1.6*10^{-19}C)\pi (1.25*10^{-3}m)^2}\\\\v_d=7.19*10^{-5}\frac{m}{s}

(c) The conductivity is given by:

\sigma=\frac{L}{RA}

You first calculate R:

R=VI=(0.86V)(5A)=4.3\Omega

Next, replace for sigma:

\sigma=\frac{50m}{(4.3\Omega)(\pi (1.25*10^{-3}m)^2)}=236881.7\Omega^{-1}m^{-1}

5 0
3 years ago
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