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3 years ago

Light energy produces the only voltage in a solar cell. (a)-True(T) (b)- false(F)

Engineering

1 answer:

Burka [1]3 years ago

7 0

Answer:

True

Explanation:

The fundamental steps involved in the operation of a solar cell are as follows:

Light is incident on the solar cell and this light energy is absorbed by the solar cell.
The absorbed energy results in the movement of the electron inside the cell which constitutes the electric current in the cell.
Electric current flows and electricity is produced.
Hence,in solar cell the light energy is responsible for the only voltage in the cell.

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. Air at 200 C blows over a 50 cm x 75 cm plain carbon steel (AISI 1010) hot plate with a constant surface temperature of 2500 C

MrRissso [65]

Answer:

The inside temperature, $T_{in}$ is approximately 248 °C.

Explanation:

The parameters given are;

Temperature of the air = 20°C

Carbon steel surface temperature 250°C

Area of surface = 50 cm × 75 cm = 0.5 × 0.75 = 0.375 m²

Convection heat transfer coefficient = 25 W/(m²·K)

Heat lost by radiation = 300 W

Assumption,

Air temperature = 20 °C

Hot plate temperature = 250 °C

Thermal conductivity K = 65.2 W/(m·K)

Steady state heat transfer process

One dimensional heat conduction

We have;

Newton's law of cooling;

q = h×A×( $T_s$ - $T_{\infty$ ) + Heat loss by radiation

= 25×0.325×(250 - 20) + 300

= 2456.25 W

The rate of energy transfer per second is given by the following relation;

$P = \dfrac{K \times A \times \Delta T}{L}$

Thermal conductivity K = 65.2 W/(m·K)

Therefore;

$2456.25 = \dfrac{65.2 \times 0.375 \times (250 - T_{in})}{0.02}$

$T_{in} = 250 - \dfrac{2456.25 \times 0.02}{65.2 \times 0.375} = 247.99 ^{\circ}C$

The inside temperature, $T_{in}$ = 247.99 °C ≈ 248 °C.

3 0

4 years ago

Discuss three objectives of Tariff and elaborate on three characteristics of it

Margaret [11]

Answer:

Three objectives of a tariff are

1) To control trade between countries

2) To protect domestic industries

3) To provide a source of income

Three characteristics of a tariff are;

1) Adequate return

2) Attractive

3) Fairness

Explanation:

A tariff is an import or export tax placed on goods traded between countries, it serves to control the foreign trade between the two countries and to protect or develop local industry

A Tariff is an important source of income to countries

Three characteristics of a tariff are;

1) Adequate return

Proper return from the consumer should be factored in a tariff to account for the alternatives or normal expense pattern

2) Attractive

The tariff should be attractive to encourage consumption of electricity or complimentary goods

3) Fairness

Based on the consumption of related resources brought about by large scale utilization, large consumer tariff should be lower than those that consume less complementary resources.

5 0

3 years ago

The 1000-lb elevator is hoisted by the pulley system and motor M. The motor exerts a constant force of 500 lb on the cable. The

klemol [59]

The power that must be supplied to the motor is 136 hp

Explanation:

Given-

weight of the elevator, m = 1000 lb

Force on the table, F = 500 lb

Distance, s = 27 ft

Efficiency, ε = 0.65

Power = ?

According to the equation of motion:

F = ma

$3(500) - 1000 = \frac{1000}{32.2} * a$

a = 16.1 ft/s²

We know,

$v^2 - u^2 = 2a (S - So)\\\\v^2 - (0)^2 = 2 * 16.1 (27-0)\\\\v = 29.48m/s$

To calculate the output power:

Pout = F. v

Pout = 3 (500) * 29.48

Pout = 44220 lb.ft/s

As efficiency is given and output power is known, we can calculate the input power.

ε = Pout / Pin

0.65 = 44220 / Pin

Pin = 68030.8 lb.ft/s

Pin = 68030.8 / 500 hp

= 136 hp

Therefore, the power that must be supplied to the motor is 136 hp

5 0

4 years ago

Who works alongside and assists the engineers?

nika2105 [10]

Answer:

Assistants works alongside and assists the engineers.

5 0

3 years ago

The flexural strength or MOR of a ceramic is 310 MPa. A block of the ceramic, which is 20 mm wide, 15 mm high, and 300 mm long,

Alja [10]

Answer:

$F=6200\ \text{N}\\$

Explanation:

In this problem you need to define the force that acts upon a beam in a 3 point bending problem. I put a picture of the problem taken from Wikipedia:

In this problem the flexural strength is defined with the following formula:

$\sigma=\cfrac{3FL}{2bd^2}$

where F is the force applied, L the length between the two rods, b the width of the ceramic block and d it's height.

The force is then defined as:

$F=\cfrac{2\sigma bd^2}{3L}=6200\ \text{N}$

3 0

3 years ago