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3 years ago

Metals are good conductors of electricity because their protons can roam freely throughout the material. True False

Physics

1 answer:

cupoosta [38]3 years ago

7 0

Answer:

Explanation:

False

Electric conductivity in metals is the result of the motion of charged particles called electrons. Atoms of metallic elements are distinguished by the availability of valence electrons. Valence electrons are the electrons in the outer shell of an atom and free to move around.

These free electrons are free to move in the lattice of metal and result in electric current when a voltage is applied.

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A bimetallic strip (brass/steel), which is straight at room temperature, will be immersed in boiling water and allowed to equili

lakkis [162]

The thermal expansion of the materials allows to find the deflection of the bimetallist strip is Δy = 3.48 cm

given paramers

* Bimetallic brass / steel tape

* Initial temperature, room temperature T = 20ºC

* Final temperature, boiling water = 100ºC

* initial length L₀ = 222mm (1cm / 10mm) = 22.2cm

* thickness of bimetallic tape e = 0.036 inch (2.54 cm/1 inch) = 0.0914 cm

to find

* perpendicular deviation or deflection (Δy)

Thermal expansion is the phenomenon of change in the length of a body due to the change in temperature, due to the increase in the length of the atomic and molecular bonds, macroscopically it is described by

ΔL = α L₀ ΔT

ΔL and ΔT are the variation of the length and temperature respectively, L₀ is the initial length and α the coefficient of expansion ends.

In this case we have a strip formed by two materials with different coefficient of thermal expansion,

Brass α_{brass} = 19 10⁻⁶ ºC⁻¹

Steel α_{steel} = 11 10⁻⁶ ºC⁻¹

In the attached we can see a diagram of the process, as the temperature increases, the material with greater thermal expansion lengthens more, so the system must curve towards the center of the material with less

thermal expansion. Let's find the length of the strip for each material

brass L_{f brass} - L₀ = α_{brass} L₀ ΔT

Steel L_{f steel} - L₀ = \alpha_{steel} L₀ ΔT

Note that the initial length is the same for the two materials and that the strip is in thermal equilibrium at room temperature.

If we assume that we have an arc of circumference, we can write the length of the arc

θ = L / r

where θ is the angle in radines, L the length of the arc and r the radius of curvature, let's write this equation for each material

brass L_{f \ brass} =θ r₁

steel L_{f \ steel} = θ r₂

we substitute in our equations

θ r₁ - L₀ = α_{brass} L₀ ΔT

θ r₂ - L₀ = α_{steel} L₀ ΔT

let's subtract the two equations

θ (r₁- r₂) = L₀ ΔT (α_{brass} - α_{steel})

the thickness of the strip is

e = r₁ -r₂

θ = $Lo \ \Delta T \ \frac{\alpha_{brass} - \alpha_{steel}}{e}$

we calculate

θ = $22.2 \ (100-20) \ \frac{(19-11) \ 10^{-6}}{0.0914}$

θ = 0.155 rad

Let's use trigonometry to find the perpendicular deflection

tan θ = Δy / L₀

Δy = L₀ tan θ

Δy = 22.2 tan 0.155

Δy = 3.48 cm

Using the thematic expansion of the two materials we find the deflection of the bimetallist strip is 3.38 cm

Learn more about thermal expansion here: brainly.com/question/18717902

7 0

2 years ago

What is the momentum of a 1,985-kg car going 32.5 m/s?

mojhsa [17]

Answer:

64512.5 m/kg

Explanation:

p=mv

p=1985 x 32.5

=64512.5

5 0

3 years ago

What is the gravitational potential energy of a 65.7 kg person standing on the roof of a 135 meter building?

horrorfan [7]

For the purpose we will use the following equation for potential energy:
U = m * g * h
In the above equation, m represents the mass of the object, h represents the height of the object and g represents the gravitational field strength (9.8 N/kg on Earth).
When we plug values into the equation, we get following:
U= 65.7kg * 9.8 N/kg *135m = 86921.1 J = 86.92 kJ

8 0

3 years ago

Compare mass and weight

netineya [11]

Answer:

The mass of an object is a measure of the object's inertial property, or the amount of matter it contains. The weight of an object is a measure of the force exerted on the object by gravity, or the force needed to support it. The pull of gravity on the earth gives an object a downward acceleration of about 9.8 m/s2.

7 0

2 years ago

(A) how much work is done when you push a crate horizontally with 100 N across a 10-m factory floor?

Mila [183]

Answer:

A) 1000 joules

Explanation:

In general work is given by the equation:

$W=\intop_{a}^{b}\overrightarrow{F}\cdot d\overrightarrow{s}$ (1)

A) With $\overrightarrow{s}$ the displacement and $\overrightarrow{F}$ the force applied, because the force and the displacement are parallel (the crate is pushed horizontally) $\overrightarrow{F}\cdot d\overrightarrow{s}$ is simply $F\,ds$ , and because the path is a straight line and the force is constant work is:

$W=FS$ (2),

$W=(100)(10)=1000\,J$

B) The work-energy theorem says that the total work on a body is equal to the change on kinetic energy:

$W_{tot}=\varDelta K$ (3)

The total work on the crate is the work done by the push and plus the work of the friction $W_{tot}=W + W_{f}$ (4) , as (A) because forces are parallel to the displacement $W= FS$ (5) and $W_{f}=-fS$ (6), the due friction always has negative sign because is opposite to the displacement, using (6), (5) and (4) on (3):

$FS-fS=\varDelta K$ (3)

$1000-(70)(10)=300\,J$

C) The energy is lost by friction, so the amount of energy turned into heat is the work the friction does:

$Q=fS=(70)(100)=700\,J$ (3)

6 0

3 years ago