/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 21 A uniform electric field exists ... [FREE SOLUTION] | 91Ó°ÊÓ

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A uniform electric field exists in the region between two oppositely charged plane parallel plates. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate, \(2.25 \mathrm{~cm}\) distant from the first, in a time interval of \(1.50 \times 10^{-6}\) s. (a) Find the magnitude of the electric field. (b) Find the speed of the proton when it strikes the negatively charged plate.

Short Answer

Expert verified
(a) Electric field \(E\) is approximately \(1.60 \times 10^3\, \text{N/C}\). (b) Speed \(v\) is approximately \(2.70 \times 10^4\, \text{m/s}\).

Step by step solution

01

Understand the Problem

We have a proton released from rest and moving under a constant electric field between two charged plates. We need to find the electric field magnitude and the speed of the proton when it reaches the negatively charged plate.
02

Given Data and Formula for Electric Field

We are given:- Distance between plates, \(d = 2.25\, \text{cm} = 0.0225\, \text{m}\) - Time interval, \(t = 1.50 \times 10^{-6}\, \text{s}\)- Initial velocity, \(v_0 = 0\, \text{m/s}\)- Mass of proton, \(m_p = 1.67 \times 10^{-27}\, \text{kg}\)- Charge of proton, \(q = 1.60 \times 10^{-19}\, \text{C}\) Using the equation of motion, we have:\[d = v_0 t + \frac{1}{2} a t^2\]Since \(v_0 = 0\), it simplifies to:\[d = \frac{1}{2} a t^2\]The electric field \(E\) can be found using \(E = \frac{F}{q} = \frac{ma}{q}\). Thus, \(a = \frac{2d}{t^2}\) will help us find \(E\).
03

Calculate Acceleration

Using equation \(d = \frac{1}{2} a t^2\), solve for \(a\):\[a = \frac{2d}{t^2} = \frac{2 \times 0.0225}{(1.50 \times 10^{-6})^2}\]Plug in the values to find \(a\).
04

Compute the Electric Field

Now, using \(a\) from the previous step, calculate the electric field \(E\) as:\[E = \frac{ma}{q}\]Substitute \(m_p\), \(a\), and \(q\) to find \(E\).
05

Calculate Speed at the Negatively Charged Plate

The final speed \(v\) of the proton can be found using kinematic equation:\[v^2 = v_0^2 + 2ad\]Since \(v_0 = 0\),\[v^2 = 2ad\]So, \[v = \sqrt{2ad}\]Using \(a\) from step 3, calculate \(v\).
06

Summary and Double Check Calculations

Summarize the values of \(E\) and \(v\) and ensure all the calculations have been correctly carried out. Double-check each step and formula for correctness.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Proton Motion
Proton motion in an electric field can be quite fascinating. When a proton, which is a positively charged particle, is released from rest, it begins to accelerate in the direction of the electric field. This is because the electric field exerts a force on the charged particle. As the proton moves, it gains speed and covers a certain distance within a specified time frame. This movement can be calculated using principles of physics that describe motion and forces.

In the given exercise, the proton starts at the surface of the positively charged plate and travels to the negatively charged plate. The time it takes to travel gives us information about the proton's acceleration. Since it starts from rest, its initial velocity is zero, making calculations for both acceleration and velocity straightforward.
Uniform Electric Field
A uniform electric field is characterized by having the same magnitude and direction at every point in a particular region. In this exercise, the uniform electric field exists between two oppositely charged parallel plates. Because the plates are parallel and large, the field between them is nearly constant. This constant field ensures that any charged particle within it, such as a proton, experiences the same force continuously as long as it remains between these plates.

Knowing the field is uniform, we can predict the behavior of charged particles like predicting the proton's path as a straight line. The uniformity also simplifies our problem-solving processes, allowing us to apply consistent values for the field strength across the entire region where calculations are made.
Electric Force on Charged Particles
When charged particles like protons are placed in an electric field, they experience an electric force. This force is calculated as the product of the charge of the particle and the electric field. Mathematically, this is expressed as \( F = qE \), where \( F \) is the force felt by the particle, \( q \) is the charge, and \( E \) is the magnitude of the electric field.

In our scenario, since we have a proton released from rest, this force is responsible for its motion. The force accelerates the proton towards the opposite charged plate due to its positive charge being attracted to the negative plate. As the proton accelerates, the magnitude of the electric field helps determine the rate of acceleration, as captured by the relevant equation involving mass, acceleration, and electric field strength.
Kinematics in Physics
Kinematics is a branch of physics that deals with the motion of objects. It focuses on parameters like displacement, velocity, acceleration, and time, without considering the causes of motion (forces). In the exercise, several kinematic principles are applied to determine how the proton moves between the plates.

The fundamental equation used for calculating acceleration in the problem is derived from the kinematic equation for uniformly accelerated motion: \[ d = v_0 t + \frac{1}{2} a t^2 \]. Here, since the proton starts from rest, \( v_0 = 0 \), simplifying to \( d = \frac{1}{2} a t^2 \). Knowing the distance \( d \) and time \( t \), we can solve for acceleration \( a \).
  • This acceleration then helps to find the electric field using \( E = \frac{ma}{q} \).
  • Also, it aids in finding the final velocity of the proton as it reaches the opposite plate using \( v = \sqrt{2ad} \).
These computations are crucial in predicting the behavior of particles under uniform electromagnetic influences.

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Most popular questions from this chapter

Torque on a Dipole. An electric dipole with dipole moment \(\vec{p}\) is in a uniform electric field \(\overrightarrow{\boldsymbol{E}}\). (a) Find the orientations of the dipole for which the torque on the dipole is zero. (b) Which of the orientations in part (a) is stable, and which is unstable? (Hint: Consider a small displacement away from the equilibrium position and see what happens.) (c) Show that for the stable orientation in part (b), the dipole's own electric field tends to oppose the external field.

In an inkjet printer, letters are built up by squirting drops of ink at the paper from a rapidly moving nozzle. The ink drops, which have a mass of \(1.4 \times 10^{-8} \mathrm{~g}\) each, leave the nozzle and travel toward the paper at \(20 \mathrm{~m} / \mathrm{s}\), passing through a charging unit that gives each drop a positive charge \(q\) by removing some electrons from it. The drops then pass between parallel deflecting plates \(2.0 \mathrm{~cm}\) long where there is a uniform vertical electric field with magnitude \(8.0 \times 10^{4} \mathrm{~N} / \mathrm{C}\). If a drop is to be deflected \(0.30 \mathrm{~mm}\) by the time it reaches the end of the deflection plates, what magnitude of charge must be given to the drop?

Excess electrons are placed on a small lead sphere with mass \(20.7 \mathrm{~g}\) so that its net charge is \(-3.20 \times 10^{-9} \mathrm{C}\). (a) Find the number of excess electrons on the sphere. (b) How many excess electrons are there per lead atom? The atomic number of lead is 82 , and its atomic mass is \(207 \mathrm{~g} / \mathrm{mol}\).

Two point charges are located on the \(y\)-axis as follows: charge \(q_{1}=-1.50 \mathrm{nC}\) at \(y=-0.600 \mathrm{~m}\), and charge \(q_{2}=\) \(+3.20 \mathrm{nC}\) at the origin \((y=0)\). What is the total force (magnitude and direction) exerted by these two charges on a third charge \(q_{3}=+5.00 \mathrm{nC}\) located at \(y=-0.400 \mathrm{~m} ?\)

Two thin rods of length \(L\) lie along the \(x\)-axis, one between \(x=a / 2\) and \(x=a / 2+L\) and the other between \(x=-a / 2\) and \(x=-a / 2-L .\) Each rod has positive charge \(Q\) distributed uniformly along its length. (a) Calculate the electric field produced by the second rod at points along the positive \(x\)-axis. (b) Show that the magnitude of the force that one rod exerts on the other is $$ F=\frac{Q^{2}}{4 \pi \epsilon_{0} L^{2}} \ln \left[\frac{(a+L)^{2}}{a(a+2 L)}\right] $$ (c) Show that if \(a \gg L, \quad\) the magnitude of this force reduces to \(F=Q^{2} / 4 \pi \epsilon_{0} a^{2} . \quad\) (Hint: Use the expansion \(\ln (1+z)=z-\) \(z^{2} / 2+z^{3} / 3-\cdots\), valid for \(|z| \ll 1\). Carry all expansions to at least order \(L^{2} / a^{2}\).) Interpret this result.

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