Ask question

Ask question

All categories

3 years ago

14

Tech A says that some starters use gear reduction to improve efficiency. Tech B says that a starter converts electrical energy t

o mechanical energy. Who is correct

1 answer:

8_murik_8 [283]3 years ago

7 0

Answer:

Explanation:

B

You might be interested in

Assume that a specific hard disk drive has an average access time of 16ms (i.e. the seek and rotational delay sums to 16ms) and

djyliett [7]

Answer:

Average access time for a hard disk = 11.38 ms

Explanation:

See attached pictures for step by step explanation.

5 0

4 years ago

A direct contact heat exchanger (where the fluid mixes completely) has three inlets and one outlet. The mass flow rates of the i

lara31 [8.8K]

Answer:

Enthalpy at outlet=284.44 KJ

Explanation:

$m_1=1 Kg/s,m_2=1.5 Kg/s,m_3=22 Kg/s$

$h_1=100 KJ/Kg,h_2=120 KJ/Kg,h_3=500 KJ/Kg$

We need to Find enthalpy of outlet.

Lets take the outlet mass m and outlet enthalpy h.

So from mass conservation

$m_1+m_2+m_3=m$

m=1+1.5+2 Kg/s

m=4.5 Kg/s

Now from energy conservation

$m_1h_1+m_2h_2+m_3h_3=mh$

By putting the values

$1\times 100+1.5\times 120+2\times 500=4.5\times h$

So h=284.44 KJ

4 0

3 years ago

(a) The room-temperature electrical conductivity of a semiconductor specimen is 13 (Ω-m)-1. The hole concentration is known to b

Aleksandr-060686 [28]

Answer: a) 0.24E+20 m-3. b) p-type extrinsic.

Explanation:

The current density in a semiconductor is composed by two types of charge carriers: electrons and holes.

This parameter, is proportional to the Electric field within the semiconductor, being the proportionality constant, the electrical conductivity of the material, that takes into account the charge carrier concentrations, and the mobility for each type.

The expression for electrical conductivity is as follows:

σ = q . ne . µe + q . np . µp

Replacing by the given values, and the value of q (charge of an electron), we can get the only unknown that remains, ne , as follows:

ne =( σ – (q . np . µp)) / q µe = (13 (Ω.m)-1 – (1.6E-19) coul(4.0E+20) m-3.0.18) m2/V-s /( (1.6E-19).0.38) coul.m2/V-s

ne = 0.24E+20.

As ne is smaller than np, this means that the semiconductor behaves like a p-type extrinsic one.

7 0

3 years ago

A horizontal opaque flat plate is well insulated on the edges and the lower surface. The top surface has an area of 8 m2 and it

Oliga [24]

Answer:

a = 0.8333

p = 0.1667

ε = 0.6243

Explanation:

Given:

- Solar Irradiation G = 6000 W

- Irradiation absorbed G_abs = 5000 W

- Heat Loss by convection Q_convec = 750 W

- The temperature of surface remains constant @ 350 K

Find:

Determine the absorptivity, reflectivity, and emissivity of the plate

Solution:

- Absorptivity is the ratio of energy absorbed to the incident energy given as:

a = G_abs / G

- Plug in values: a = 5000 / 6000

a = 0.8333

- Reflectivity is the ratio of energy not absorbed to the incident energy given as:

p = (1 - G_abs) / G

- Plug in values: p = 1000 / 6000

p = 0.1667

- Emissivity is the of ratio amount energy that is radiated from the body to the black body:

- We will use energy balance on the plate surface:

E_in - E_out = -k*A*dT / L

- We know that the plate temperature remains constant, dT = 0:

E_in = E_out

Q_abs = Q_convec + Q_rad

Q_rad = Q_abs - Q_convec

- Plug in values: Q_rad = 5000 - 750 = 4250 W

- The expression for surface radiation is given by:

Q_rad = ε*A*б*T_b^4

- Re-arrange: ε = Q_rad / A*б*T_b^4

- Plug values in: ε = 4250 / 8*(5.67*10^-8)*(350)^4

ε = 0.6243

4 0

3 years ago

Tech A says that LED brake lights illuminate faster than incandescent bulbs. Tech B says that LED brake lights have

nikdorinn [45]

Answer:

Both

Explanation:

3 0

3 years ago