Ask question

Ask question

All categories

3 years ago

6

A 100-watt light bulb illuminates a solar cell. The electricity from the solar cell operates a water pump that delivers 1 watt o

f power. What is the efficiency of the system?

1 answer:

Ann [662]3 years ago

5 0

Answer:

1 %

Explanation:

The efficiency of a system is defined as the ratio between the energy produced and the energy in input:

$\eta = \frac{E_{out}}{E_{in}}\cdot 100$

The same formula can also be rewritten in terms of the power produced and the power in input:

$\eta = \frac{P_{out}}{P_{in}}\cdot 100$

Since in this problem we have:

$P_{in}=100 W\\P_{out}=1 W$

The efficiency is

$\eta = \frac{1 W}{100 W}\cdot 100$ =1 \%

You might be interested in

Scheduling comes before sequencing. In scheduling, we develop plans for our work centers where production activities occur. We l

ser-zykov [4K]

Answer: 89

Explanation:

4 0

3 years ago

Three identical resistors are connected in parallel to a battery. If the current of 12. A flows from the battery, how much curre

Doss [256]

Answer:

4 A

Explanation:

We are given that

$R_1=R_2=R_3=4\Omega$

I=12 A

We have to find the current flowing through each resistor.

We know that in parallel combination current flowing through different resistors are different and potential difference across each resistor is same.

Formula :

$\frac{1}{R}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}$

Using the formula

$\frac{1}{R}=\frac{1}{4}+\frac{1}{4}+\frac{1}{4}=\frac{3}{4}$

$R=\frac{4}{3}\Omega$

$V=IR$

Substitute the values

$V=12\times \frac{4}{3}=16 V$

$I_1=\frac{V}{R_1}=\frac{16}{4}=4 A$

$I_1=I_2=I_3=4 A$

Hence, current flows through any one of the resistors is 4 A.

7 0

3 years ago

A force of 48 newtons is required to start a 5.0 kg box moving across a horizontal concrete floor. What is the coefficient of st

Soloha48 [4]

1) The coefficient of static friction is 0.980

2) The coefficient of kinetic friction is 0.908

Explanation:

1)

In the first situation, the box is still at rest. There are two forces acting on the box:

- The force of push, F, forward

- The force of static friction, $F_f$

Since the box is in equilibrium we have

$F_f = F$ (1)

The value of frictional force changes from zero to a maximum value which is given by:

$F_f = \mu_s mg$ (2)

where

$\mu_s$ is the coefficient of static friction

m is the mass of the box

g is the acceleration of gravity

So, if the force F needed to put the box in motion is 48 N, it means that this is also the maximum value of the force of friction. So, we can combine eq.(1) and (2) to find the coefficient of static friction:

$\mu_s = \frac{F}{mg}$

where:

F = 48 N

m = 5.0 kg

$g=9.8 m/s^2$

Substituting,

$\mu_s = \frac{48}{(5.0)(9.8)}=0.980$

2)

In this second situation, the object is already in motion, so the equation of motion is:

$F-F_f = ma$

where

F = 48 N is the force applied forward

$a = 0.70 m/s^2$ is the acceleration of the box

$F_f = \mu_k mg$ is the force of kinetic friction, where

$\mu_k$ is the coefficient of kinetic friction

We can therefore rearrange the equation to find the coefficient:

$F-\mu_k mg = ma\\\mu_k mg = F-ma\\\mu_k = \frac{F-ma}{mg}=\frac{48-(5.0)(0.70)}{(5.0)(9.8)}=0.908$

Learn more about friction:

brainly.com/question/6217246

brainly.com/question/5884009

brainly.com/question/3017271

brainly.com/question/2235246

#LearnwithBrainly

7 0

3 years ago

What kind of lens is there in our eyes? where does it form the image of an object?

Goshia [24]

Answer:

convex lens

Explanation:

An image is form in retina with light rays converging most at cornea and upon entering and existing the lens.Rays from top and bottom of the object are traced and produce an inverted image on the retina

8 0

3 years ago

Which planets are visible without a telescope

Annette [7]

The planet MARS is visible without a telescope on many clear nights. The planets JUPITER, MERCURY, VENUS and SATURN are also viewable without the aid of magnification.

3 0

3 years ago