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
lozanna [386]
3 years ago
7

You have 10 ohm and a 100 ohm resistor in parallel. You place this equivalent resistance in series with an LED, which is rated t

o have a voltage drop of 1.83V at 20mA. What voltage should you connect to this circuit to provide 20mA of current for the LED? What would the current be, if you connected to a 3V battery? Draw all of these diagrams before attempting the calculations.
Physics
1 answer:
Nataly [62]3 years ago
7 0

Answer:

Approximately \rm 2.0\; V.

Approximately \rm 30 \; mA. (assumption: the LED here is an Ohmic resistor.)

Explanation:

The two resistors here R_1= 10\; \Omega and R_2= 100\; \Omega are connected in parallel. Their effective resistance would be equal to

\displaystyle \frac{1}{\dfrac{1}{R_1} + \dfrac{1}{R_2}} = \frac{1}{\dfrac{1}{10} + \dfrac{1}{100}} = \frac{10}{11} \; \Omega.

The current in a serial circuit is supposed to be the same everywhere. In this case, the current through the LED should be 20\; \rm mA = 0.020\; \rm A. That should also be the current through the effective \displaystyle \rm \frac{10}{11} \; \Omega resistor. Make sure all values are in standard units. The voltage drop across that resistor would be

V = I \cdot R = 0.020 \times \dfrac{10}{11} \approx 0.182\; \rm V.

The voltage drop across the entire circuit would equal to

  • the voltage drop across the resistors, plus
  • the voltage drop across the LED.

In this case, that value would be equal to 1.83 + 0.182 \approx 2.0\; \rm V. That's the voltage that needs to be supplied to the circuit to achieve a current of 20\; \rm mA through the LED.

Assuming that the LED is an Ohmic resistor. In other words, assume that its resistance is the same for all currents. Calculate its resistance:

\displaystyle R(\text{LED}) = \frac{V(\text{LED})}{I(\text{LED})}= \frac{1.83}{0.020} \approx 91.5\; \Omega.

The resistance of a serial circuit is equal to the resistance of its parts. In this case,

\displaystyle R = R(\text{LED}) + R(\text{Resistors}) = 91.5 + \frac{10}{11} \approx 100\; \Omega.

Again, the current in a serial circuit is the same in all appliances.

\displaystyle I = \frac{V}{R} = \frac{3}{100} \approx 0.030\; \rm A = 30\; mA.

You might be interested in
A balloon is filled at sea level on a spring day (temperature 20°C) to a volume of 0.500 m3 and then brought at op of Mount Ever
blagie [28]

Answer:

Volume increases

Explanation:

The balloon when filled at sea level being comparatively close to the center of the earth will have higher pressure due to the influence of gravity and when this balloon is taken to the top of the mountain being away from the center of earth, it will experience a lesser pressure due to low gravity where the amount of force exerted by the air on the object is lesser as compared to to that at the sea level.

Therefore, there will be an increase in volume of the balloon as there is expansion of air on the inside of the balloon as a result of low pressure.

There is not  much effect of temperature at both the sea level and the mountain top as the temperature does not impart any energy to the air molecules so as to decrease the volume.

Therefore,there is an increase in the volume of the balloon at the top of the mountain.

Percentage change in volume is given by:

% change = \farc{V - 0.5}{0.5}times 100

8 0
3 years ago
A 5000kg freight car moving at 2 m/s East collides with a 10,000kg freight car at rest. Upon collision, they got stuck and moved
mr_godi [17]

Answer:

A

Explanation:

6 0
3 years ago
Aerogenerators are used to produce electricity from
ki77a [65]
Like windmills they use the winds to generate their power.
4 0
3 years ago
A grandfather clock is "losing" time because its pendulum moves too slowly. Assume that the pendulum is a massive bob at the end
IgorC [24]

Answer:

d) shortening the string

Explanation:

Time period of a pendulum clock is dependent on two factors namely:length and acceleration due to gravity.

When a clock loses time, the time period of the pendulum clock increases.

This however can be corrected by decreasing the length of the pendulum.The time period of the pendulum clock is not dependent on the mass of the bob. The time period of the pendulum clock can be corrected only by changing the length of the pendulum string.

5 0
3 years ago
Read 2 more answers
Physics double pivot question​
andriy [413]

Explanation:

Assuming the wall is frictionless, there are four forces acting on the ladder.

Weight pulling down at the center of the ladder (mg).

Reaction force pushing to the left at the wall (Rw).

Reaction force pushing up at the foot of the ladder (Rf).

Friction force pushing to the right at the foot of the ladder (Ff).

(a) Calculate the reaction force at the wall.

Take the sum of the moments about the foot of the ladder.

∑τ = Iα

Rw (3.0 sin 60°) − mg (1.5 cos 60°) = 0

Rw (3.0 sin 60°) = mg (1.5 cos 60°)

Rw = mg / (2 tan 60°)

Rw = (10 kg) (9.8 m/s²) / (2√3)

Rw = 28 N

(b) State the friction at the foot of the ladder.

Take the sum of the forces in the x direction.

∑F = ma

Ff − Rw = 0

Ff = Rw

Ff = 28 N

(c) State the reaction at the foot of the ladder.

Take the sum of the forces in the y direction.

∑F = ma

Rf − mg = 0

Rf = mg

Rf = 98 N

3 0
3 years ago
Other questions:
  • How does energy from an ocean wave power stuff in a house?
    12·1 answer
  • A rocket with mass m traveling with speed v0 along the x axis suddenly shoots out one-third its mass parallel to the y axis (as
    14·1 answer
  • A hot–air balloon is moving at a speed of 10.0 meters/second in the +x–direction. The balloonist throws a brass ball in the +x–d
    10·1 answer
  • The reason an astronaut in an earth satellite feels weightless is thatThe reason an astronaut in an earth satellite feels weight
    11·2 answers
  • In separate experiments, a large number of particles (all with the same charge, but with a wide variety of masses and speeds) ar
    9·1 answer
  • In a physics laboratory experiment, a coil with 250 turns enclosing an area of 14 cm2 is rotated in a time interval of 0.030 s f
    9·1 answer
  • 4.
    6·1 answer
  • In the far future, astronauts travel to the planet Saturn and land on Mimas, one of its 62 moons. Mimas is small compared with t
    11·1 answer
  • What is a solenoid
    6·2 answers
  • In which situation does the reactive force between two colliding objects cause a physical change? (1 point)
    8·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!