What is Power dissipated: Definition and 72 Discussions
In electrical engineering, the maximum power transfer theorem states that, to obtain maximum external power from a source with a finite internal resistance, the resistance of the load must equal the resistance of the source as viewed from its output terminals. Moritz von Jacobi published the maximum power (transfer) theorem around 1840; it is also referred to as "Jacobi's law".The theorem results in maximum power transfer across the circuit, and not maximum efficiency. If the resistance of the load is made larger than the resistance of the source then efficiency is higher, since a higher percentage of the source power is transferred to the load, but the magnitude of the load power is lower since the total circuit resistance increases.If the load resistance is smaller than the source resistance, then most of the power ends up being dissipated in the source, and although the total power dissipated is higher, due to a lower total resistance, it turns out that the amount dissipated in the load is reduced.
The theorem states how to choose (so as to maximize power transfer) the load resistance, once the source resistance is given. It is a common misconception to apply the theorem in the opposite scenario. It does not say how to choose the source resistance for a given load resistance. In fact, the source resistance that maximizes power transfer from a voltage source is always zero, regardless of the value of the load resistance.
The theorem can be extended to alternating current circuits that include reactance, and states that maximum power transfer occurs when the load impedance is equal to the complex conjugate of the source impedance.
Recent expository articles illustrate how the fundamental mathematics of the maximum power theorem also applies to other physical situations, such as:
mechanical collisions between two objects,
the sharing of charge between two capacitors,
liquid flow between two cylinders
the transmission and reflection of light at the boundary between two media
Homework Statement
High power lasers in factories are used to cut through cloth and metal. One such laser has a beam diameter of 1.5mm and generates an electric field at the target having an amplitude of .854MV/m.
speed of light= 3.0e8 m/s
permeability of free space is 4pi x 10-7 TN/A
What...
Homework Statement
A power station delivers 750 kW of power at 12,000 V to a factory through wires with total resistance 3.0 ohms. How much less power is wasted if the electricity is delivered at 50,000 V rather than 20,000 V?
Homework Equations
P = IV = (I^2)(R) = (V^2)/R
The...
hello
Find the power dissipated in the (6 ohm) resistor.
the circuit is in the attachments
i know that P in the resistor = (i^2)*R
but how can i find the current in that 6 ohm resistor?
thanks
Homework Statement
A zener diode runs off 10V and supplies 5V to a load that draws 100mA. The minumum zener current = 5mA. R = 47Ω What is the dissipation in the resistor if the output is short-circuited?
Homework Equations
None.
The Attempt at a Solution
Using R = V - Vz / Izmin...
I am trying to plot the graphs of power dissipated in pure resistor , pure capacitor and pure inductor against time .
My question is when i plot the voltage and current graph for pure resistor , i know they are in the same phase , but V0 is greater or Io is greater , i think Vo is greater...
Homework Statement
In a different RLC circuit the generator provides a voltage V(t) = 120 sin(2π60t) so that the current in the circuit is I(t) = 5 sin(2π60t +Φ). The phase angle Φ is 25° (0.436 radians). What is the maximum power dissipated in this circuit?
Homework Equations
P = IV...
Homework Statement
Using symbols, write PRL, the power dissipated in RL as a function of RL (your other symbols are R0 and the power supply voltage epsilon both of which are constant. 10V and 100ohms) and then take the derivative of this function with respect to RL for which PRL has an extreme...
Homework Statement
I understand the maths... I'm here to ask WHY we have to do it this way.
The question states:
"The power dissipated in a resistor is given by P= E^2/R. If E=200 and R=8 , find the change in P resulting in a drop of 5 Volts in E and an increase of 0.2 Ohms in...
Homework Statement
For this sample exam, we are given an RLC circuit, with an alternative emf of 1 V, connected all in series with a 500 ohm resistor, a .4 mH inductor, and two capacitors in parallel of 50 pF each.
It asks for the "maximum power dissipated by the resistance" and at what...
Homework Statement
A cylindrical cavity oriented along z axis with length of 2 m has a filament in it upon which a current of 10 A is impressed. Cavity is perfectly conducting whereas it is filled with lossy dielectric. Electric field on the cavity is given as: E=-z(i+j). One has to...
Homework Statement
What is the power dissipated by the 5.0Ω resistor in the following circuit?
Homework EquationsI thought maybe to simplify the resistance like.
1/r=1/30 +1/30
r=15
+10+5
R=30ohms
then find the current
v=ir
25=Ix30
I=.8333
then find power with the 5 ohms?
P=vi
P=25x5...
Homework Statement
How much power is dissipated by the 12\Omega resistor in the figure?
PR1=______W
How much power is dissipated by the 18 resistor in the figure?
PR2=______W
Homework Equations
P=IV
I=\frac{V}{R}
The Attempt at a Solution
P=\frac{V}{R}*V
P=V2/R...
In RL, AC circuit, an AC source vst = 220sin(40000t-45°) is connected to a 60mH inductor and a 3kΩ resistor.
Show that the power dissipated in the inductor is zero.
The current in this circuit is 0.057A as I calclulated. I know that inductor has no charging role in this circuit. But...
Resistor & power dissipated question--please help
Homework Statement
Load resistor R is attached to a battery with EMF E and internal resistance r. For what value of the resistance R in terms of E and r will the power dissipated by the load resistor be a maximum?
Homework Equations...
Hi all,
I'm doing a lab now to determine the relationship between the resistance of a resistor (colour-coded ones) and the energy and power dissipated. What kind of relationship is expected between the variables R and P, or R and E?
The way I carried out the lab was to use different...
Homework Statement
(See attachment for diagram)
Known Values:
R1 = 5
R2 = 15
R3 = 25
R4 = 5
V1 = 40
V2 = 20
I1 = 71/7
I2 = 25/7
I3 = 4
1) Find the power dissipated in each resistor
2) Find the power associated with each voltage source including the independent
source and...
Homework Statement
The corroded contacts in a lightbulb socket have 8 Ω total resistance.How much actual power is dissipated by a 126 W (115 V) lightbulb screwed into the socket?
Homework Equations
P = I*V
I = E/R
The Attempt at a Solution
I = 115/8 = 14.375
I don't know how to...
Can someone give me a reply Intro Physics style? :D
P = IV is known as the "power of the circuit" right?
But then, we have questions asking about the heat dissipated by a resistor. We can use P = IV, P=I^2 R , or P=V^2/R to answer such questions
Since the voltage drops all add up to...
a charged capacitor has capacitance C and charge Q. a resistor R is then connected what is the power dissipated right after the connection?
V=Q/C
so P=V^2/R=Q^2/(RC^2)
is this right?
what is the power dissipated in the resistor when the energy stored in the capacitor has decreased to...
Greetings,
I recently took an introductory circuits test. The answer key was released today. I am convinced it's wrong, and if my argument is flawed, I'd like to know before bringing it up with the instructor (no, not the professor, the BME guy who appears to apply equations without actually...
An RLC series circuit constists of a resistor of 100 ohm, a capacitor of 10.0uF, and an inductor of 0.250 H. The circuit is connected to a power supply of 120 V and 60 Hz. What is the power dissipated in the circuit?
I got 37 W (rounding 2 S.F's)
the solutions manual has the answer as 73 W...