I\'m not understanding the parts underlined in red. (1) When I put my thumb in t
ID: 1436648 • Letter: I
Question
I'm not understanding the parts underlined in red. (1) When I put my thumb in the direction of current (up), and curl my fingers (direction of B), it points to *me*, and not into the page, as the book says. (2) Also, how do they know that E is pointing down? (3) Furthermore if I is pointing up and E is pointing down, this makes them *not* mutually perpendicular..but the book says that I, E, and B are all mutually perpendicular. Why?
three-quarters of a cycle, at t-, as shown in Figure 25-1 (f). Immediately after this time, the electric field begins to point downward once more. The net result is a wavelike electric field moving steadily away from the antenna. To summarize: A current flowing in an antenna... The electric field produced by an antenna connected to an ac gener- ator propagates away from the antenna, analogous to a wave on a string moving away from your hand as you wiggle it up and down. E.produces This is really only half of the electromagnetic wave, however; the other half is a similar wave in the magnetic field. To see this, consider Figure 25-2, where we show the current in the antenna flowing upward at a time when the upper seg both electric and magnetic fields. ment is positive. Pointing the thumb of the right hand in the direction of the cur-FIGURE 25-2 Field directions in an rent, and curling the fingers around the wire, as specified in the magnetic fie electromagnetic wave At a time when the electric field pro- duced by the antenna points downward the magnetic field points into the page. In general, the electric and magnetic we see that B points into the page at the same time that E points downwar It follows, then, that E and B are at right angles to each other. A more detailed are perpendicular to each other at all times, and that and thatIn general analysis shows that E and B they are also in phase; that is, when the magnitude of E is at its maximum, so is fields in an electromagnetic wave are the magnitude of B always at right angles to each other Combining the preceding results, we can represent the electric and magnetic fields in an electromagnetic wave as shown in Figure 25-3. Notice that not only are Combining tromagnetie wave ashown in Figure 25-3 Notice that not only arePhysisExplanation / Answer
the field at any point is an the direction of curl. field is into plane only at right to the wire but it is out of plane to the left of the wire. the field is the tangent to the curl.
E is always from positive charge to negative charge
in any. there will not be the statement that I and E are perpandicular. but B is perpandicular to both I and E. so recheck it