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The current of an electron beam has a measured current of \(I=50.00 \mu \mathrm{A}\) with a radius of \(1.00 \mathrm{mm}^{2}\) What is the magnitude of the current density of the beam?

Short Answer

Expert verified
The magnitude of the current density of the electron beam is \(50.00 \, \mathrm{A/m^2}\).

Step by step solution

01

Convert the given values to base SI units

Current (I): 50.00 渭A = 50.00 脳 10鈦烩伓 A Area (A): 1.00 mm虏 = 1.00 脳 10鈦烩伓 m虏
02

Calculate the current density

Use the formula J = I / A to find the current density. J = (50.00 脳 10鈦烩伓 A) / (1.00 脳 10鈦烩伓 m虏)
03

Simplify the expression

Cancel out the common factor 10鈦烩伓 in both the numerator and the denominator. J = 50.00 A/m虏 The magnitude of the current density of the electron beam is 50.00 A/m虏.

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Key Concepts

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

SI Units Conversion
Before solving physics problems, it's essential to ensure all values are in proper SI units. This common practice helps maintain consistency and accuracy.
For the given exercise, we have two measurements to convert:
  • Current, originally in microamperes (\(\mu A\)), needs to be in amperes (A). Since 1 \(\mu A = 10^{-6}\text{A}\), multiply 50.00 \(\mu A\) by \(10^{-6}\) to convert it to amperes. This results in \(50.00 \times 10^{-6} \text{ A}\)
  • Area, originally in square millimeters (\(\text{mm}^2\)), needs to be in square meters (m虏). Knowing \(1\text{mm} = 10^{-3}\text{m}\), you square this conversion for area, resulting in \(1\text{mm}^2 = 10^{-6}\text{m}^2\)
These conversions allow us to accurately use the given numbers in any formula requiring SI base units.
Electron Beam Current
Understanding what electron beam current is can offer insight into various applications of physics. In this scenario, the current (\(I\)) relates to the flow of electrons in the beam.
Electron beam current is the amount of charge passing through a particular point in the beam per unit of time. Measured in amperes (A), it's crucial to express it in this unit when calculating further parameters.
For this problem, the current of the electron beam is 50.00 \(\mu A\). After performing the SI unit conversion, we have \(50.00\times 10^{-6}\text{ A}\), leading us closer to computing the current density. This concept is essential in activities like creating X-rays or designing cathode ray tubes, where precise control of electron current is needed.
Current Density Formula
Current density is a measure of the electric current per unit area of cross-section. In simpler terms, it's how densely packed the electric current is in a given area. The formula is given by \(J = \frac{I}{A}\), where \(J\) represents current density, \(I\) is the current, and \(A\) is the cross-sectional area.
Calculating current density in the exercise involves dividing the electron beam current, \(50.00\times 10^{-6}\text{ A}\), by the area of \(1.00\times 10^{-6} \text{ m}^2\). By substituting and simplifying, we arrive at a value: \(J = 50.00 \text{ A/m}^2\).
Understanding this concept is vital in fields like electronics and material science, where current density helps determine material performance and efficiency. The higher the current density, the more current flows through an area, typically requiring more robust materials or heat dissipation management.

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Most popular questions from this chapter

In this chapter, most examples and problems involved direct current (DC). DC circuits have the current flowing in one direction, from positive to negative. When the current was changing, it was changed linearly from \(I=-I_{\max }\) to \(I=+I_{\max }\) and the voltage changed linearly from \(V=-V_{\max }\) to \(V=+V_{\max },\) where \(V_{\max }=I_{\max } R\) Suppose a voltage source is placed in series with a resistor of \(R=10 \Omega\) that supplied a current that alternated as a sine wave, for example, \(I(t)=(3.00 \mathrm{A}) \sin \left(\frac{2 \pi}{4.00 \mathrm{s}} t\right)\) What would a graph of the voltage drop across the resistor \(V(t)\) versus time look like? (b) What would a plot of \(V(t)\) versus \(I(t)\) for one period look like? (Hint: If you are not sure, try plotting \(V(t)\) versus \(I(t)\) using a spreadsheet.)

(a) To what temperature must you raise a copper wire, originally at \(20.0^{\circ} \mathrm{C},\) to double its resistance, neglecting any changes in dimensions? (b) Does this happen in household wiring under ordinary circumstances?

The current through a 12 -gauge wire is given as \(I(t)=(5.00 \mathrm{A}) \sin (2 \pi 60 \mathrm{Hz} t) .\) What is the current density at time \(15.00 \mathrm{ms} ?\)

The IR drop across a resistor means that there is a change in potential or voltage across the resistor. Is there any change in current as it passes through a resistor? Explain.

What is the resistance of a 20.0 -m-long piece of 12-gauge copper wire having a 2.053 -mm diameter?

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