1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
zhuklara [117]
3 years ago
14

A cylindrical metal rod has a resistance . If both its length and its diameter are quadrupled, its new resistance will be:______

__.
A. 16R
B. R/4
C. R
D. 4R
Physics
1 answer:
N76 [4]3 years ago
8 0

Answer:

R' = R/4

Explanation:

The resistance of a metal rod is R. It is given by the relation as follows :

R=\rho\dfrac{l}{A}

Where

l is the length and A is the area of cross-section

A=\pi r^2=\pi (\dfrac{d}{2})^2

If both its length and its diameter are quadrupled, it means,

l' = 4l

and d'= 4d

It means,

A'=\pi (\dfrac{4d}{2})^2

Let new resistance be R'. So,

R'=\rho\dfrac{l'}{A'}\\\\R'=\rho\dfrac{4l}{\pi (\dfrac{4d}{2})^2}\\\\=\rho \dfrac{4l}{\pi \dfrac{16d^2}{2}}\\\\=\dfrac{4}{16}\times \dfrac{\rho l}{\pi \dfrac{d^2}{2}}\\\\=\dfrac{1}{4}\times \dfrac{\rho l}{\pi \dfrac{d^2}{2}}\\\\R'=\dfrac{R}{4}

So, the correct option is (B) "R/4".

You might be interested in
The driver of a car slams on the brakes when he sees a tree blocking the road. the car slows uniformly with acceleration of -5.9
Hatshy [7]
Let u =  the speed of the car at the instant when braking begins.

The braking distance is s = 62.3 m, the acceleration is a = -5.9 m/s², and the braking duration is t = 4.15 s.

Use the formula s = ut + (1/2)at² to obtain
(u m/s)*(4.15 s) + 0.5*(-5.9 m/s²)*(4.5 s)² = (62.3 m)
4.15u = 62.3 + 50.8064 = 113.1064
      u = 27.2546 m/s

Let v m/s be the speed with which the car strikes the tree.
Then
v = 27.2546 - 5.9*4.15
   = 2.7696 m/s

Answer: 2.77 m/s (nearest hundredth)

4 0
3 years ago
Where does salt in the ocean come from
Bingel [31]

Answer:

Salt in the ocean comes from two sources: runoff from the land and openings in the seafloor. Rocks on land are the major source of salts dissolved in seawater. Rainwater that falls on land is slightly acidic, so it erodes rocks.

5 0
3 years ago
Read 2 more answers
Assume an axon has an internal diameter of 1μm and a myelin sheath 1μm thick. The internal specific resistance is 100 Ω cm. For
SpyIntel [72]

Answer:

1.27\times 10^{12}\Omega/m

Explanation:

We are given that

Diameter=d=\mu m

Thickness=1\mu m

Radius=r=\frac{d}{2}=\frac{1}{2}\mu m=0.5\times 10^{-6} m

Using 1\mu m=10^{-6} m

Dielectric constant=8

Resistance =R=2\times 10^5\Omega cm^2

Internal specific resistance=r=100 ohm cm=100\times \frac{1}{100}\Omega-m=1\Omega m

Using 1 m=100 cm

Internal resistance per unit length=\frac{r}{A}=\frac{1}{\pi r^2}=\frac{1}{3.14\times (0.5\times 10^{-6})^2}=1.27\times 10^{12}\Omega/m

Using \pi=3.14

Internal resistance per unit length=1.27\times 10^{12}\Omega/m

8 0
3 years ago
How do bones and muscles work together to allow movement?
alexandr1967 [171]
I believe the answer is A

7 0
3 years ago
Read 2 more answers
A uniform horizontal rod of mass Mand length rotates with angular velocity about a vertical axis through its center. Attached to
Lostsunrise [7]

Answer:

     o

90

Explanation:

3 0
3 years ago
Other questions:
  • When 1.14 g of octane (molar mass = 114 g/mol) reacts with excess oxygen in a constant volume calorimeter, the temperature of th
    8·1 answer
  • An AC generator has an output rms voltage of 100.0 V at a frequency of 42.0 Hz. If the generator is connected across a 45.0-mH i
    10·1 answer
  • Like electric charges repel each other. T F
    14·2 answers
  • A 900 N crate is being pulled across a level floor by a force F of 340 N at an angle of 23° above the horizontal. The coefficien
    14·1 answer
  • Unpolarized light is passed through an optical filter that is oriented in the vertical direction. 1) If the incident intensity o
    8·1 answer
  • An eletric pump in the ground floor
    12·1 answer
  • Which technology has allowed for space exploration
    11·2 answers
  • If Goku sprints and tackles a large metal crate doing 18002 J of work over the course of
    11·1 answer
  • Is the force of gravity that attracts my body to the Earth related to the force of gravity between the planets and the Sun
    8·1 answer
  • You are traveling at 55 mi/h along the x-axis relative to a straight, level road and pass a car that is traveling at 45 mi/h. Th
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!