Ch. 19 Flashcards
(6 cards)
The fact that the electron has a negative charge and the proton has a positive charge is due to a convention established by Benjamin Franklin. Would there have been any significant consequences if Franklin had chosen the opposite convention? Is there any advantage to naming charges plus and minus as opposed to A and B?
No.
When the current existing convention for the charge for the electron and proton is interchanged, then there is no effect at all because the net charge in the universe is the same.
If charges were replaced by A and B then we would have trouble defining zero because the zero means that an object has an equal number of positive and negative charges.
A proton moves in a region of constant electric field. Does it follow that the protons velocity is parallel to the electric field? Does it follow that the protons acceleration is parallel to the electric field? Explain.
The proton can move in any direction relative to the constant electric field because mainly it depends upon the angle by which it enters into the electric field.
The protons acceleration must be parallel to the electric field direction. This is because the electrostatic force and the electric field will both be in the same direction for a positive charge.
A system consists of two charges of equal magnitude and opposite sign separated by a distance d. Since the total electric charge of this system is zero can we conclude that the electric field produced by the system is also zero? Does your answer depend on the separation d? Explain.
Consider two equal and opposite charges separated by finite distance d. The net charge of the system will be zero. However, it cannot be concluded that the net electric field produced by this system will be zero. For example, consider a point which is closer to the positive charge. Now the electric field at this point will be the vector sum of electric fields due to both positive and negative charge. Since the point is closer to positive charge than the negative charge, magnitude of the electric field due to positive charge will be greater than magnitude of electric field due to negative charge. Therefore, after the vector sum, the effective electric field will be positive.
If the separation becomes negligible, the net electric field can be said to be zero as both the charges will have equal and opposite electric fields at the point under consideration.
The force experienced by charge 1 at point A is different in direction and magnitude from the force experienced by charge 2 at point B. Can we conclude that the electric fields at point A and B are different? Explain.
The direction and magnitude of the force at point A from charge q1 and at point B from charge q2 are different. This means the sign and magnitude of the charges may be different, but their corresponding electric field must be the same at their respective points.
Can an electric field exist in a vacuum? Explain
Electromagnetic fields exist in solids, liquids, gases and the vacuum. In the vacuum the electromagnetic field propagates this gas a component of electric and magnetic field.
YES, the electric field exists in a vacuum. Best example is the sun. The sun is a giant ball of nuclear reactions which creates not just light but a large range of electromagnetic fields. Atmosphere absorbs some of this energy and the spinning of the earths gigantic core creates a huge magnetic field around the earth. This field points in the direction of one of the magnetic poles. At the poles of the earth, the magnetic field passes through the earth. Therefore the field is smaller and causes the aurora borealis, the interaction of the suns electromagnetic energy without atmosphere.
Gauss’s law can tell us how much charge is contained within a gaussian surface. Can it tell us where inside the surface it is located? Explain.
No the electric flux through a surface depends on the total charge enclosed by the surface but it is completely independent of location of the enclosed charges. Hence Gauss law cannot tell us the location of the charges.
