1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
sukhopar [10]
3 years ago
8

A battery with an emf of 12.0 V shows a terminal voltage of 11.7 V when operating in a circuit with two lightbulbs, each rated a

t 4.0 W (at 12.0 V), which are connected in parallel.
What is the battery's internal resistance?
Physics
2 answers:
wariber [46]3 years ago
5 0
<h2>Answer:</h2>

0.46Ω

<h2>Explanation:</h2>

The electromotive force (E) in the circuit is related to the terminal voltage(V), of the circuit and the internal resistance (r) of the battery as follows;

E = V + Ir                      --------------------(a)

Where;

I = current flowing through the circuit

But;

V = I x Rₓ                    ---------------------(b)

Where;

Rₓ = effective or total resistance in the circuit.

<em>First, let's calculate the effective resistance in the circuit:</em>

The effective resistance (Rₓ) in the circuit is the one due to the resistances in the two lightbulbs.

Let;

R₁ = resistance in the first bulb

R₂ = resistance in the second bulb

Since the two bulbs are both rated at 4.0W ( at 12.0V), their resistance values (R₁ and R₂) are the same and will be given by the power formula;

P = \frac{V^{2} }{R}

=> R = \frac{V^{2} }{P}             -------------------(ii)

Where;

P = Power of the bulb

V = voltage across the bulb

R = resistance of the bulb

To get R₁, equation (ii) can be written as;

R₁ = \frac{V^{2} }{P}    --------------------------------(iii)

Where;

V = 12.0V

P = 4.0W

Substitute these values into equation (iii) as follows;

R₁ = \frac{12.0^{2} }{4}

R₁ = \frac{144}{4}

R₁ = 36Ω

Following the same approach, to get R₂, equation (ii) can be written as;

R₂ = \frac{V^{2} }{P}    --------------------------------(iv)

Where;

V = 12.0V

P = 4.0W

Substitute these values into equation (iv) as follows;

R₂ = \frac{12.0^{2} }{4}

R₂ = \frac{144}{4}

R₂ = 36Ω

Now, since the bulbs are connected in parallel, the effective resistance (Rₓ) is given by;

\frac{1}{R_{X} } = \frac{1}{R_1} + \frac{1}{R_2}       -----------------(v)

Substitute the values of R₁ and R₂ into equation (v) as follows;

\frac{1}{R_X} = \frac{1}{36} + \frac{1}{36}

\frac{1}{R_X} = \frac{2}{36}

Rₓ = \frac{36}{2}

Rₓ = 18Ω

The effective resistance (Rₓ) is therefore, 18Ω

<em>Now calculate the current I, flowing in the circuit:</em>

Substitute the values of V = 11.7V and Rₓ = 18Ω into equation (b) as follows;

11.7 = I x 18

I = \frac{11.7}{18}

I = 0.65A

<em>Now calculate the battery's internal resistance:</em>

Substitute the values of E = 12.0, V = 11.7V and I = 0.65A  into equation (a) as follows;

12.0 = 11.7 + 0.65r

0.65r = 12.0 - 11.7

0.65r = 0.3

r = \frac{0.3}{0.65}

r = 0.46Ω

Therefore, the internal resistance of the battery is 0.46Ω

Studentka2010 [4]3 years ago
4 0

Answer:

R_i_n_t=0.45 \Omega

Explanation:

Internal resistance is a concept that helps model the electrical consequences of the complex chemical reactions that occur within a battery. When a charge is applied to a battery, the internal resistance can be calculated using the following equation:

R_i_n_t=(\frac{V_N_L}{V_F_L} -1)R_L

Where:

V_F_L=Load\hspace{3}voltage=11.7V\\V_N_L= O pen\hspace{3}circuit\hspace{3}voltage=12V\\R_L=Load\hspace{3}resistance

As you can see, we don't know the exactly value of the R_L. However we can calculated that value using the next simple operations:

The problem tell us that the power of each lightbulb is 4.0 W at 12.0 V, hence let's calculated the power at 11.7V using Cross-multiplication:

\frac{12}{11.7} =\frac{4}{P}

Solving for P :

P=\frac{11.7*4}{12} =3.9W

Now, the electric power is given by:

P=\frac{V^2}{R_b}

Where:

R_b=Resistance\hspace{3}of\hspace{3}each\hspace{3}lightbulb

So:

R_b=\frac{V^2}{P} =\frac{11.7^2}{3.9} =35.1\Omega

Now, because of the lightbulbs are connected in parallel the equivalent resistance is given by:

\frac{1}{R_L} =\frac{1}{R_b} +\frac{1}{R_b} =\frac{2}{R_b} \\\\ R_L= \frac{R_b}{2} =\frac{35.1}{2}=17.55\Omega

Finally, now we have all the data, let's replace it into the internal resistance equation:

R_i_n_t=(\frac{12}{11.7} -1)17.55=0.45\Omega

You might be interested in
) Continuing on Problem 1, assume a strain gage was bonded to the cylinder wall surface in the direction of the axial strain. Th
zzz [600]

Answer:

See attached document

Explanation:

Entire process for deriving the asked expression dV across the bridge as function of dP is illustrated in the attachment below.

The document gives a step-by step process for arriving at the expression. However, manipulation of algebraic equations is skipped for the conciseness of the document.

It also gives the expression for the case when all resistors have different nominal values.

Download docx
6 0
3 years ago
According to Newton’s law of universal gravitation, which statements are true?
andreyandreev [35.5K]

Before we solve this, we should know this fact:

According to Newton's Law of Gravitation, the force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The force acts along the line joining the centres of the two objects. It can be shown by this:

F ∝ \frac{Mm}{ {d}^{2} }

Now, let us check all the options.

A. As we move to higher altitudes, the force of gravity on us decreases.

<em>This </em><em>statement </em><em>is </em><em>true.</em>

The force of gravity is inversely proportional to the square of distance from the centre of the earth. If, we go up the surface of the earth, the distance from the centre of the earth increases and hence the value of force of gravity decrease. So, force of gravity decreases with altitude.

B. As we move to higher altitudes, the force of gravity on us increases.

<em>This </em><em>statement</em><em> </em><em>is </em><em>false.</em>

We have already got the result in option A. that the force of gravity decreases with altitude. It never increases with altitude.

C. As we gain mass, the force of gravity on us decreases.

<em>This </em><em>statement</em><em> </em><em>is </em><em>false.</em>

The force of gravity is directly proportional to the product of the masses. So, if increase our mass, then the force of gravity will also increase and if we decrease our mass, then the force of gravity decreases.

D. As we gain mass, the force of gravity on us increases.

<em>This </em><em>statement</em><em> is</em><em> </em><em>true.</em>

As mentioned earlier in option C., the force of gravity is directly proportional to the product of the masses of the earth and another object. So, as we gain mass, the force of gravity on us increases.

E. As we move faster, the force of gravity on us increases.

<em>This </em><em>statement</em><em> is</em><em> </em><em>true</em><em>.</em>

Here, we have to consider a different formula. According to Newton's Second Law,

F = ma, where F is the force, m is the mass and a is the acceleration.

In other words,

F ∝ a, i.e., force is directly proportional to acceleration.

We know, acceleration is the rate of change of velocity of an body within a time period.

So, if speed is increased, then acceleration will also be greater, which results in the increase of force. So, as we move faster, the force of gravity on us increases.

<u>Answers:</u>

A: As we move to higher altitudes, the force of gravity on us decreases.

D: As we gain mass, the force of gravity on us increases.

E: As we move faster, the force of gravity on us increases.

Hope you could understand.

If you have any query, feel free to ask.

7 0
2 years ago
CAN someone help ASAP?
lyudmila [28]

Answer:someone help me

Explanation:

7 0
3 years ago
What is the change all living things undergo as the grow
Vladimir [108]
All of the change that living things undergo as they grow is called development. That is the name when the changes are within a single unit and over a period of time as short as a lifetime. When the change occurs over thousands of years then it's called evolution.
6 0
3 years ago
The motion of a free falling body is an example of __________ motion​
swat32

Answer:

accelerated

Explanation:

The motion of the body where the acceleration is constant is known as uniformly accelerated motion. The value of the acceleration does not change with the function of time.

4 0
3 years ago
Read 2 more answers
Other questions:
  • jill picked 65 apples at a local orchard. 20% of the apples were green apples . How many apples did jill pick
    10·2 answers
  • The mass of an electron is 9.11×10−31 kg. If the de broglie wavelength for an electron in a hydrogen atom is 3.31×10−10 m
    14·1 answer
  • This problem describes an experimental method for determining the moment of inertia of an irregular shaped object such as the pa
    8·1 answer
  • when we touch a steel rod and a paper simultaneously we feel that the rod is comparatively colder .why?
    13·1 answer
  • 20 A measure of the speed and direction of an object's motion
    7·1 answer
  • When four people with a combined mass of 310 kg sit down in a 2000-kg car, they find that their weight compresses the springs an
    5·1 answer
  • PLEASE HELP!!<br> What is osteoporosis? What are the symptoms and treatments?
    5·2 answers
  • Which is moving faster a car traveling 150 km in 3 hours or one traveling 100 km in 2 hours?
    11·1 answer
  • What are some examples of non-inertial reference frames?
    8·1 answer
  • The tensile stress in a thick copper bar is 99.5 % of its elastic breaking point of 13.0× 10¹⁰ N/m² . If a 500-Hz sound wave is
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!