What is Field strength: Definition and 367 Discussions

In physics, field strength means the magnitude of a vector-valued field (e.g., in volts per meter, V/m, for an electric field E).
For example, an electromagnetic field results in both electric field strength and magnetic field strength.
As an application, in radio frequency telecommunications, the signal strength excites a receiving antenna and thereby induces a voltage at a specific frequency and polarization in order to provide an input signal to a radio receiver. Field strength meters are used for such applications as cellular, broadcasting, wi-fi and a wide variety of other radio-related applications.

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  1. jlmccart03

    Find electric field strength expression for a specfic region

    Homework Statement A thick, spherical shell of inner radius a and outer radius b carries a uniform volume charge density ρ. Find an expression for the electric field strength in the region a<r<b. Homework Equations Gauss's Law ∫E⋅dA Area of a sphere The Attempt at a Solution I know I am...
  2. jlmccart03

    Electric field strength near a metal plate

    Homework Statement A total charge of 21 μC is applied to a thin, 1μm square metal plate 72 cm on a side. Find the electric field strength near the plate's surface, far from the edges. Homework Equations I think E = kq/r^2, but I really don't know. The Attempt at a Solution I am...
  3. D

    I Why do the extra terms cancel in the derivation of the EM field strength tensor?

    Hi I am trying to follow the derivation in some notes I have for the field strength tensor using covariant derivatives defined by Du = ∂u - iqAu . The field strength is the defined by [ Du , Dv ] = -iqFuv The given answer is Fuv = ∂uAv - ∂vAu .When I expand the commutator I get this...
  4. T

    B Relating Gravitational Field Strength and Mass

    I know the formula for calculating field strength is g= GM/r2 , however if I'm trying to show the proportionality relationship between just g and m, would g ∝ m be correct, since a larger mass equals a stronger force of gravity and vice versa?
  5. D

    I Covariant derivative of field strength tensor

    Hi, I am struggling to derive the relations on the right hand column of eq.(4) in https://arxiv.org/pdf/1008.4884.pdfEven the easy abelian one (third row) which is $$D_\rho B_{\mu\nu}=\partial_\rho B_{\mu\nu}$$ doesn't match my calculation Since $$D_\rho B_{\mu\nu}=(\partial_\rho+i g...
  6. Clara Chung

    Question of latitude of Earth and measured field strength

    Homework Statement My book said: As the Earth is rotating about its axis, objects on the Earth's surface are performing circular motion. Therefore, objects on the Earth are accelerating and they need a centripetal force. The weight contributes a small portion to the centripetal force needed...
  7. H

    Finding where the gravitational field strength is 0

    1. Homework Statement Homework Equations g = (Gm)/r2 The Attempt at a Solution I tried doing (Gm1)/a2 = (Gm2)/(r-a)2 where a is equal to the distance from the position we're trying to find to the center of the most massive object but end up getting a quadratic in the denominator on the right...
  8. S

    Distance of compass to wire based on magnetic field strength

    Homework Statement As shown in Figure 1 below, a long, straight conducting wire is stretched horizontally directly above a magnetic compass, both of which are separated by distance d. When electrical current is not flowing through the wire, the compass needle points in a direction parallel with...
  9. Matticus9

    Calculating Electric Field Strength of a Charged Metal Sphere

    Homework Statement A metal sphere with a diameter of 10 cm has a charge distribution of 1.09085 x 1018 electrons/cm2 on its surface. What is the electric field strength at a distance of 25 cm from the surface of the sphere? (Answer: 5.5 x 1012 N/C) Homework Equations I wasn't given any...
  10. D

    A CP properties of field strength tensor

    Hi, I am trying to figure out why a term like ## L \sim i \bar \psi_L \sigma^{\mu\nu}G_{\mu\nu}^a t^a \psi_R + h.c=## ##= i \bar \psi_L \sigma^{\mu\nu}G_{\mu\nu}^a t^a \psi_R - i \bar \psi_R \sigma^{\mu\nu}G_{\mu\nu}^a t^a \psi_L ## violates CP by looking at all the terms composing the...
  11. S

    Electric field strength with distance

    Consider Gauss's law in ##1## space and ##1## time dimension. In this case, ##\int\ \vec{E}\cdot{d\vec{A}}=\displaystyle{\frac{Q}{\epsilon_{0}}} \implies 2 E =\displaystyle{\frac{Q}{\epsilon_{0}}} \implies E =\displaystyle{\frac{Q}{2\epsilon_{0}}}##, where the factor of ##2## comes from the...
  12. B

    Magnetic field strength over distance

    I want to know how does distance affect the magnetic field of a permanent magnet. I have read about the inverse square law and how it could apply to magnetic fields over growing distances, but doing so, I read about monopoles, which is a new concept to me. So, for the time being, I would like a...
  13. Zack K

    Gravitational field strength at a point

    Homework Statement What is the gravitational field strength at a point 6.38x106 m above the Earth's surface? Homework Equations The Attempt at a Solution Ok so I plug in all the known variables. G= 6.67x10-11. M= 5.98x1024. r= 6.38x106 and so I multiply that by 2 because the given point is...
  14. petrushkagoogol

    I Field strength variation of different types of fields

    The field strength of gravitational, electric and magnetic fields vary as the inverse square of the distance from the source. Is this because all of the above fields are generated by fermions and they behave identically regardless of the nature of the fields ? Do the above fermions have rest...
  15. H

    B Gravitational field strength calculation

    In what scenarios would you use the equation g= F/m instead of g=GM/r2 (or vice versa), for calculating gravitational field strength? Update: is g=F/m used to find the force acting on a mass in a gravitational field (of strength g), whereas g=GM/r2 used to calculate the gravitational field...
  16. 1

    Why does the point experience NEGATIVE field strength?

    Hi, i'm looking for an explanation to this answer of a past paper that I'm doing, it's from OCR (A level) G485, question 1 b ii) the question on top, and answer on bottom i don't understand why would the point experience a negative electric field strength when it's getting closer to a...
  17. C

    Electric field strength at a point between charges

    Homework Statement A +1.0 μC charge is placed at point X. A +4.0 μC charge is placed at point Y, 50 cm from X. How far from X, on the line XY, is the point where the electric field strength is zero? Homework Equations E = Q/4πε0r2 The Attempt at a Solution I know that the electric field is...
  18. RobertColman

    How can I derive a formula for change in B field strength?

    I'm a bit stuck on this question (which is homework so hints are more welcome than outright answers). The question is: A very long wire carrying a current I is moving with speed v towards a small circular wire loop of radius r. The long wire is in the plane of the loop and is too long to be...
  19. S

    Magnetic field strength for circular loop

    When deriving the magnetic field strength due to a circular loop at some distance away from it's center (using Biot-Savart's law), why is the angle between ds and r 90 degrees? This is a youtube video with the derivation, see 5:55
  20. J

    Electric field strength in metal sphere

    1. Homework Statement Why is there no electric field strength in a metal sphere? Is it because the sum of the individial electric field strength of the charges in the sphere is zero? How is that possible? Homework EquationsThe Attempt at a Solution
  21. L

    Electric field at a point inside of a uniformly charged ball

    As the name of the thread says, I am wondering what would the amount and the direction of the electric field at some point in the uniformly charged ball of radius R(it has a constant charge volume density) be at the distance r from the centre of the ball. Does anyone know what would they be? I...
  22. K

    Is this how to attempt this problem on electric field strength

    Homework Statement Two parallel plates at -50kV and 100kV have separation 35cm. a proton is placed between the plates. calculate the electric field strength between the plates Homework Equations E=v/d The Attempt at a Solution 100kV--50kV=150kV 150x10^3/0.35=428571.4N/C
  23. A

    Graphs of Gravitational Potential and Field Strength

    Hi all, I am very confused about the graphs of gravitational potential and gravitational field strength... I know that both gravitational field (g) and electric field strength (E) are negative gradient of their corresponding potential (Vg and Ve). If so, shouldn't g and Vg graph look very much...
  24. S

    Electromagnet magnetic field strength

    Homework Statement Homework Equations ##\oint_{C} Bd\ell = \mu I_{enc}, B_{normal}## continuous across boundary, ##H_{parallel}## continuous across boundary The Attempt at a Solution $$\oint_{C} Bd\ell = \mu I_{enc} \rightarrow B = \frac{\mu NI}{2\pi r}$$ Any help much appreciated. How...
  25. Physics Dad

    Electric Field Strength - Assignment Question

    Homework Statement The Nucleus of a helium ion contains two protons approximately 5x10-15m apart. They can be considered to be surrounded by one orbiting electron approximately 5x10-11m away. Calculate the following: a) The electrostatic force between the two protons b) The electrostatic...
  26. henrco

    Find the rms electric field strength of a given EM wave

    Hi, I was able to correctly calculate the answer to part 1 below but the answer to part 2 is incorrect and I cannot see the error of my ways... any help gratefully received. 1. Homework Statement An electromagnetic wave has an intensity of 127 W/m2. 1) Find its rms electric field strength...
  27. K

    Uniform electric field - tension & electric field strength

    Homework Statement A ball with a mass of 3.0 x 10-4 kg hangs from a 15 cm long thread between two parallel plates. The thread is deflected to the side, as shown in the following diagram. The charge on the ball is +5.0 x 10-5 C. a) Find the tension in the thread b) Find the magnitude and...
  28. Y

    What is the electric field strength inside the capacitor?

    Homework Statement [/B] An electron is launched at a 45∘ angle and a speed of 5.0×10^6 m/s from the positive plate of the parallel-plate capacitor shown in the figure (Figure 1) . The electron lands 4.0 cm away. a) What is the electric field strength inside the capacitor? b) What is the...
  29. A

    Can we apply Friss equation to find field strength at the receiving point....

    Can we apply friss equation to find field strength at the receiving point for space wave propagation?
  30. Einstein's Cat

    Gravitational Field Strength of 1

    To note this is not for any piece of homework. Anyway, what possible masses and a distance between them are required for there to be a gravitational field strength of 1 Newtons per kilograms, when these figures are put into Newton's equation of F= G (m1 * m2 / r sqaured) Many thanks!
  31. kostoglotov

    How electric fields store energy in a capacitor

    Homework Statement The Question is here: imgur link: http://i.imgur.com/wIlUZMM.jpg Homework Equations U_c = \frac{\kappa \epsilon_0 A d E^2}{2} U_c = C \Delta V_c \kappa: dielectric constant \epsilon_0: permittivity of free space C: capacitance The Attempt at a Solution [/B] I...
  32. E

    Magnetic field strength at point P around a solenoid

    I have a solenoid, Length L, number of turns N, ampers I Radius R I have a Point P(x,y,z) anywhere around said solenoid. How can I calculate the field strength at point P, note it is OUTSIDE the solenoid, and could be anywhere outside. Assume the origin is the center of the solenoid, let's...
  33. darida

    Components of The Electromagnetic Field Strength Tensor

    Source: http://gmammado.mysite.syr.edu/notes/RN_Metric.pdf Section 2 Page: 2 Eq. (15) The radial component of the magnetic field is given by B_r = g_{11} ε^{01μν} F_{μν} Where does this equation come from? Section 4 Page 3 Similar to the electric charges, the Gauss's flux theorem for the...
  34. 1

    Electric Field Strength Question

    I already posted this, but it was on the wrong section. This is from the 2009 HSC exam. (I'm in Australia) I checked the answers and found that electric field strength was E = 100/0.10 = 1000V/m My question is, what would the electric field strength be if the positively charged plate was...
  35. Murdock

    Calculating field strength of an electromagnet

    I would like to build an electromagnet to accelerate electrons into a circle (a precursor to a mass spectrometer). I would like to calculate the field strength, but I don't know how because I would like to wind it out of aluminum strap salvaged from a welder, and I can only find formulas for...
  36. P

    Electric field strength from x=-a to x = a

    Homework Statement I attached a file. Numbers 10 and 12. Homework Equations kQq/r, kQq/r^2 The Attempt at a Solution I am confused about this problem. Shouldn't the electric field strength be 0 when x = 0? The charges are opposite and adding two opposite vectors with equal magnitude should...
  37. SquidgyGuff

    Distance independence of electric field strength

    I was just wondering why the strength of the electric fields of insulating surface charges like sheets and shells aren't dependent on the distance from the charge according to Gauss's Law?
  38. B

    Formula of Average Magnetic B Field Strength of Large Conductor

    Any one knows how to calculate the magnetic B field strength at a distance from a Large Conductor ? Do we go by average ? thanks
  39. Corey Bacon

    Electric field strength between two disks?

    Homework Statement Two 3.0 cm diameter disks face each other, 1.9mm apart. They are charged to $$\pm 16nC$$. (a). What is the field strength between the disks? (b). A proton is shot from the negative disk toward the positive disk, what launch speed must the proton have to barely reach the...
  40. F

    Calculating field strength mV/m at distance d - check me

    it's been awhile for me so check if I'm remembering this right... Thanks. electric field strength is inversely proportional to distance squared... right? So if the electric field strength is 1,000 mV/m at 1 meter then the following is true... right? km______mV/m________ the math 1________1000...
  41. C

    Covariant derivatives commutator - field strength tensor

    Homework Statement So I've been trying to derive field strength tensor. What to do with the last 2 parts ? They obviously don't cancel (or do they?) Homework EquationsThe Attempt at a Solution [D_{\mu},D_{\nu}] = (\partial_{\mu} + A_{\mu})(\partial_{\nu} + A_{\nu}) - (\mu <-> \nu) =...
  42. T

    Calculate gravitational field strength above surface of Mars

    1. Calculate the gravitational field strength at 500km above Mars' surface. Mass of Mars: 6.39 x 1023 kg Radius of Mars: 3.39 x 103 km Constant G: 6.67 x 10-11 2. I used the equation g = GM / r23. To begin with I added the 500km height above ground to the radius, giving 3.89 x 103 km. I then...
  43. A

    Hall Effect Probe for Measuring Magnetic Field Strength

    Homework Statement In a probe that uses the Hall effect to measure magnetic fields, a 11-A current passes through a 1.33-cm-wide and 1.31-mm-thick strip of sodium metal. If the Hall emf is 2.42 μV, what is the magnitude of the magnetic field (take it perpendicular to the flat face of the...
  44. J

    Finding the magnetic field strength

    Homework Statement There exists a current of 5A in the ay direction at x=2m,z=-2m where the ay is the unit vector in the y direction. Find the magnetic field strength at the origin. Homework Equations B = (μI/2πR) * r B = μH The Attempt at a Solution B = (μI/2πr) B= (4π*10^-7)(5)/2π(2) where...
  45. Euler2718

    Solenoid Field Strength - Missing Raduis?

    Homework Statement A long solenoid has 35 turns/cm. With a current of 4.0A, what is the field strength at the core? Homework Equations \beta = \frac{\mu N I}{2r} The Attempt at a Solution I have no idea with the radius is; that's the entire problem statement above.
  46. R

    Deriving the electromagnetic field strength tensor

    Just one last question today if someone can help. I'm trying to derive the electromagnetic field strength tensor and having a little trouble with (i think) the use of identities, please see below: I understand the first part to get -Ei, but it's the second line of the next bit I don't...
  47. T

    Gravitational field strength of a mass

    A 20 kg mass is situated 4m above the Earth's surface Taking g as 10 m/s2. What are the gravitational field strength and gravitational force acting on the mass? Am I wrong when I say that because the height of the mass ( which is 4m) is too little comparing with the radius of the Earth so that...
  48. D

    Could Earth's Early Magnetic Field Have Trapped Hydrogen in the Atmosphere?

    could Earth's early magnetic field have been strong enough to trap hydrogen within the atmosphere?
  49. pyman999

    What is the mistake in my calculation for gravitational field strength?

    Homework Statement Homework Equations g = GM / r^2, where g is the gravitational field strength, G is the gravitational constant, M is the mass of the attracting body, r is the radius of the attracting body. p = M / v, where p is density and v is the volume. Vs = 4/3 * pi * r^3, where Vs is...
  50. D

    Problem in Magnetic Field and magnetic effect of electric current

    I read in class 10. I am having problem understanding magnetic fields, magnetic flux,magnetic flux density,magnetic field strength,magnetic permeability and strength of magnetic field produced due to a straight and closed loop current carrying conductor at a certain point at a certain distance...
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