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1 year ago

How can three resistors of resistance 2ohm,3ohm and 6ohm be connected to go live total resistance of (a) 4ohm,(b)1ohm?

Physics

1 answer:

Sophie [7]1 year ago

8 0

$\sf\large \green{\underbrace{\red{Answer⋆}}}:$

(a) R2, R3 are parallel and series with R1

(b) R1, R2 and R3 are in parallel

Explanation:

$\sf R_1 = 2 \: ohm\\ \sf R_2 = 3 \: ohm \\ \sf R_3 = 6 \: ohm$

(a)

$\sf R_2 \: and \: R_3 \: are \: in \: parallel \\ \sf so \: let \: the \: total \: of \: R_2 \: and \: R_3 \: be \: R_a$

$\sf \large \frac{1}{R_a} = \frac{1}{R_2} + \frac{1}{R_3} \: as \: they \: are \: in \: parallel$

$\sf R_a = \frac{1}{3} + \frac{1}{6} \\ \\ \sf \frac{1}{R_a} = \frac{2 + 1}{6} \\ \\ \sf \frac{1}{R_a} = \frac{3}{6} \\ \\ \sf \frac{1}{R_a} = \frac{1}{2} \\ \\ \sf R_a = 2 \: ohm$

Ra and R1 is in series

And there total will be R

$\sf R = R_a + R_1 \\ \\ \sf R = 2 + 2 \\ \\ \sf R = 4 \: ohm$

(b)

$\sf R_1 R_2 \: and \:R_3 \: are \: in \: parallel \: so \: total \: be \: R$

$\sf \frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} \\ \\ \sf \frac{1}{R} = \frac{1}{2} + \frac{1}{3} + \frac{1}{ 6} \\ \\ \sf \frac{1}{R} = \frac{3+ 2 +1 }{6} \\ \\ \sf \frac{1}{R} = \frac{6}{6} \\ \\ \sf R = 1 \: ohm$

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2 years ago

Determine the power that needs to besupplied by the fanifthe desired velocity is 0.05 m3/s and the cross-sectional area is 20 cm

Mariulka [41]

Answer:

A fan with an energy efficiency of 30 % would need 62.5 watts to bring a desired volume flow of 0.05 cubic meters per second through a cross-sectional area of 20 square centimeters.

Explanation:

Complete statement is: Determine the power that needs to besupplied by the fan if the desired velocity is 0.05 cubic meters per second and the cross-sectional area is 20 square centimeters.

From Thermodynamics and Fluid Mechanics we know that fans are devices that work at steady state which accelerate gases (i.e. air) with no changes in pressure. In this case, mechanical rotation energy is transformed into kinetic energy. If we include losses due to mechanical friction, the Principle of Energy Conservation presents the following equation:

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Where:

$\eta$ - Efficiency of fan, dimensionless.

$\dot W$ - Electric power supplied fan, measured in watts.

$\dot K$ - Rate of change of kinetic energy of air in time, measured in watts.

From definition of kinetic energy, the equation above is now expanded:

$\dot W = \frac{\rho_{a}\cdot \dot V}{2\cdot \eta}\cdot \left(\frac{\dot V}{A_{s}} \right)^{2}$ (Eq. 2)

Where:

$\rho_{a}$ - Density of air, measured in kilograms per cubic meter.

$\dot V$ - Volume flow, measured in cubic meters per second.

$A_{s}$ - Cross-sectional area of fan, measured in square meters.

If we know that $\rho_{a} = 1.20\,\frac{kg}{m^{3}}$ , $\dot V = 0.05\,\frac{m^{3}}{s}$ , $\eta = 0.3$ and $A_{s} = 20\times 10^{-4}\,m^{2}$ , the power needed to be supplied by the fan is:

$\dot K = \left[\frac{\left(1.20\,\frac{kg}{m^{3}} \right)\cdot \left(0.05\,\frac{m^{3}}{s} \right)}{2\cdot (0.3)} \right]\cdot \left(\frac{0.05\,\frac{m^{3}}{s} }{20\times 10^{-4}\,m^{2}} \right)^{2}$

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A fan with an energy efficiency of 30 % would need 62.5 watts to bring a desired volume flow of 0.05 cubic meters per second through a cross-sectional area of 20 square centimeters.

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3 years ago

A catapult launches a test rocket vertically upward from a well, giving the rocket an initial speed of 80.6 m/s at ground level.

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Answer:

44.64 seconds

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$v=u+at\\\Rightarrow 128.01=80.6+4.2t\\\Rightarrow t=\frac{128.01-80.6}{4.2}=11.29\ s$

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Time the rocket will keep going up after the engines shut off is 13.06 seconds.

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The rocket will fall from this height

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Time taken by the rocket to fall from maximum height is 20.29 seconds

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2 years ago

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svet-max [94.6K]

Answer:

4:28

Explanation:

4:28am

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2 years ago

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Lapatulllka [165]

Answer:

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Explanation:

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X-rays have higher frequency than radio waves. --> TRUE, as we can see from the table above.

X-rays have shorter wavelengths than radio waves. --> TRUE, as we can see from the table above.

X-rays travel through space faster than radio waves. --> FALSE: all electromagnetic waves travel in space at the same speed, the speed of light.

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2 years ago

How can three resistors of resistance 2ohm,3ohm and 6ohm be connected to go live total resistance of (a) 4ohm,(b)1ohm?​

How can three resistors of resistance 2ohm,3ohm and 6ohm be connected to go live total resistance of (a) 4ohm,(b)1ohm?