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3 years ago

A material through which a current does not move easily is a(n) _____.

1 answer:

6 0

<span>A material through which a current does not move easily is called
an insulator.

Technically, charges CAN move through an insulator, but they lose
a lot of energy doing it, so the current that flows through the insulator
is very very small, usually too small to even measure.

Another way to look at it: Insulators have high resistance.
</span>

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Air at 400 kPa, 980 K enters a turbine operating at steady state and exits at 100 kPa, 670 K. Heat transfer from the turbine occ

Angelina_Jolie [31]

Answer:

a). $\frac{\dot{W}}{m}= 311$ kJ/kg

b). $\frac{\dot{\sigma _{gen}}}{m}=0.9113$ kJ/kg-K

Explanation:

a). The energy rate balance equation in the control volume is given by

$\dot{Q} - \dot{W}+m(h_{1}-h_{2})=0$

$\frac{\dot{Q}}{m} = \frac{\dot{W}}{m}+m(h_{1}-h_{2})$

$\frac{\dot{W}}{m}= \frac{\dot{Q}}{m}+c_{p}(T_{1}-T_{2})$

$\frac{\dot{W}}{m}= -30+1.1(980-670)$

$\frac{\dot{W}}{m}= 311$ kJ/kg

b). Entropy produced from the entropy balance equation in a control volume is given by

$\frac{\dot{Q}}{T_{boundary}}+\dot{m}(s_{1}-s_{2})+\dot{\sigma _{gen}}=0$

$\frac{\dot{\sigma _{gen}}}{m}=\frac{-\frac{\dot{Q}}{m}}{T_{boundary}}+(s_{2}-s_{1})$

$\frac{\dot{\sigma _{gen}}}{m}=\frac{-\frac{\dot{Q}}{m}}{T_{boundary}}+c_{p}ln\frac{T_{2}}{T_{1}}-R.ln\frac{p_{2}}{p_{1}}$

$\frac{\dot{\sigma _{gen}}}{m}=\frac{-30}{315}+1.1ln\frac{670}{980}-0.287.ln\frac{100}{400}$

$\frac{\dot{\sigma _{gen}}}{m}=0.0952+0.4183+0.3978$

$\frac{\dot{\sigma _{gen}}}{m}=0.9113$ kJ/kg-K

5 0

3 years ago

Please help, and show steps. Thank you very much!

Vikentia [17]

V = 8 * 10^2 km/h = 800km/h
S= 1,8* 10^3 km = 1800km
t = ?
v = S/t
t = S/v
t = 1800km/ 800km/h
t ≈ 2,25h (135min)

6 0

3 years ago

a man throws a football straight into the air. As it rises,it slows down. Which type of energy is the football gaining?

kotykmax [81]

It is gaining potental energy which will then transfer to knetic energy as it falls

5 0

3 years ago

Read 2 more answers

A metal rod 80cm long lengthens by 0.090cm when its temperature rises by 93.6$^o$C. What is the linear expansivity of the metal

alexandr1967 [171]

Answer: (b)0.000012/k

Explanation:

The linear expansion of the metal rod is given by

$\Delta L= L_0 \alpha \Delta T$

where

$\Delta L=0.090 cm$ is the linear expansion

$L_0 = 80 cm$ is the initial length of the rod

$\alpha$ is the linear expansivity

$\Delta T=93.6^{\circ}C=93.6 K$ is the increase in temperature

By re-arranging the equation, we find the linear expansivity:

$\alpha = \frac{\Delta L}{L_0 \Delta T}=\frac{0.090 cm}{(80 cm)(93.6K)}=0.000012 K^{-1}$

8 0

3 years ago

in vision, the ____ stream controls identification of an object, and the ____ stream controls action toward the object.

prisoha [69]

Answer: In vision, the ventral stream controls identification of an object, and the dorsal stream controls action toward the object.

Explanation: The ventral stream is associated with object recognition and form representation.

Dorsal stream a pathway that carries visual information from the primary visual cortex to the parietal lobe.

Hope it helps :)

7 0

2 years ago