Ask question

Ask question

All categories

3 years ago

8

A fuse in an electric circuit is a wire that is designed to melt, and thereby open the circuit, if the current exceeds a predete

rmined value. Suppose that the material to be used in a fuse melts when the current density rises to 500 A/cm2. What diameter of cylindrical wire should be used to make a fuse that will limit the current to 0.64 A?

1 answer:

zmey [24]3 years ago

8 0

Answer:

The diameter of wire should be $4.04 \times 10^{-4}$ m

Explanation:

Given:

Current density $J = 500 \times 10^{4}$ $\frac{A}{m^{2} }$

Current $I = 0.64$ A

From the formula of current density,

$J = \frac{I}{A}$

Where $A =$ area of cylindrical wire = $\pi r^{2}$

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

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

$r = \sqrt{\frac{0.64}{3.14 \times 500 \times 10^{4} } }$

$r = 2.02 \times 10^{-4}$ m

For finding the diameter of wire,

$d = 2r$

$d = 4.04 \times 10^{-4}$ m

Therefore, the diameter of wire should be $4.04 \times 10^{-4}$ m

You might be interested in

A transformer is intended to decrease the value of the alternating current from 500 amperes to 25 amperes. The primary coil cont

EastWind [94]

Answer:

The number of turns in secondary coil is 4000

Explanation:

Given:

Current in primary coil $I_{P} = 500$ A

Current in secondary coil $I_{S} = 25$ A

Number of turns in primary coil $N_{P} = 200$

In case of transformer the relation between current and number of turns is given by,

$\frac{N_{S} }{N_{P} } = \frac{I_{P} }{I_{S} }$

For finding number of turns in secondary coil,

$N_{S} = \frac{I_{P} }{I_{S} } N_{P}$

$N_{S} = \frac{500}{25} \times 200$

$N_{S} = 4000$

Therefore, the number of turns in secondary coil is 4000

5 0

3 years ago

The table represents the speed of a car in a northern direction over several seconds. A 2-column table with 5 rows. The first co

Oksanka [162]

Answer:

Column 1 should be titled “Time,” and Column 2 should be titled

“Velocity.” ⇒ 1st answer

Explanation:

* <em>Lets revise some definitions of graphs</em>

A velocity-time graph represents the speed and direction an object

travels over a period of time.

Velocity-time graph is called speed-time graph.

The vertical axis of a velocity-time graph represents the velocity of the

object and horizontal axis represents the time from the initial position

In an acceleration time graph y-axis represents the acceleration, and

x-axis represents the time

The table represents the <em>speed of a car in a northern</em> direction over

several seconds

That means the data in the table represent the <em>velocity</em> of the car in a

certain time

Time (s) Velocity (m/s)

0 5

2 10

4 15

6 20

8 25

10 30

Column 1 would be on the x-axis

x-axis represents the time

Column 2 would be on the y-axis

y-axis represents the velocity

Column 1 should be titled “Time,” and Column 2 should be titled

“Velocity.”

3 0

3 years ago

Read 2 more answers

At an altitude of 5000 m the rocket's acceleration has increased to 6.9 m/s2 . What mass of fuel has it burned?

sergey [27]

1) Initial upward acceleration: $6.0 m/s^2$

2) Mass of burned fuel: $0.10\cdot 10^4 kg$

Explanation:

1)

There are two forces acting on the rocket at the beginning:

- The force of gravity, of magnitude $F_g = mg$ , in the downward direction, where

$m=1.9\cdot 10^4 kg$ is the rocket's mass

$g=9.8 m/s^2$ is the acceleration of gravity

- The thrust of the motor, T, in the upward direction, of magnitude

$T=3.0\cdot 10^5 N$

According to Newton's second law of motion, the net force on the rocket must be equal to the product between its mass and its acceleration, so we can write:

$T-mg=ma$ (1)

where a is the acceleration of the rocket.

Solving for a, we find the initial acceleration:

$a=\frac{T-mg}{m}=\frac{3.0\cdot 10^5-(1.9\cdot 10^4)(9.8)}{1.9\cdot 10^4}=6.0 m/s^2$

2)

When the rocket reaches an altitude of 5000 m, its acceleration has increased to

$a'=6.9 m/s^2$

The reason for this increase is that the mass of the rocket has decreased, because the rocket has burned some fuel.

We can therefore rewrite eq.(1) as

$T-m'g=m'a'$

where

$m'$ is the new mass of the rocket

Re-arranging the equation and solving for m', we find

$m'=\frac{T}{g+a}=\frac{3.0\cdot 10^5}{9.8+6.9}=1.8\cdot 10^4 kg$

And since the initial mass of the rocket was

$m=1.9 \cdot 10^4 kg$

This means that the mass of fuel burned is

$\Delta m = m-m'=1.9\cdot 10^4 - 1.80\cdot 10^4 = 0.10\cdot 10^4 kg$

3 0

3 years ago

How do magnetic forces repel or attract?

Lerok [7]

“Magnets are surrounded by an invisible magnetic field that is made by the movement of electrons, the subatomic particles that circle the nucleus of an atom”

“Every magnet has both a north and a south pole. When you place the north pole of one magnet near the south pole of another magnet, they are attracted to one another. When you place like poles of two magnets near each other (north to north or south to south), they will repel each other.”

3 0

3 years ago

An area experiences thunderstorms with high winds and a drop in temperature. Which weather event most likely occurred? A. A stat

gavmur [86]

Answer:

C a fast-moving cold front moved through the area.

Explanation:

This is because, since there is a there is a thunderstorm and high winds in the area, this can only be caused by a fast moving front. Also there is a temperature drop, this can only be caused by the fast moving cold front since a cold front has a low temperature.

Thus, for the area to experience thunderstorms with high winds and a drop in temperature, <u>a fast-moving cold front moved through the area.</u>

5 0

3 years ago