Direction of Electric Field in a Changing Magnetic Field

AI Thread Summary
In a scenario with a decreasing magnetic field directed out of the page, Lenz's Law indicates that the induced electric field will oppose this change. The discussion reveals confusion regarding the direction of the electric field, with the initial assumption suggesting it should point towards the top of the page due to the right-hand rule, while the answer key indicates it points downwards. Participants agree that the induced magnetic field should also point out of the page, leading to a counterclockwise current. The consensus is that the electric field direction aligns with the current flow, supporting the initial reasoning. Overall, the correct interpretation of the electric field's direction remains a point of contention but leans towards the bottom of the page based on the provided answer key.
Queequeg
Messages
24
Reaction score
0

Homework Statement



In a circular region in the plane of paper, a magnetic field is directed out of the page and decreasing. What is the direction of the electric field at a point to the right of the region?

Homework Equations



Lenz's law

The Attempt at a Solution



Since the magnetic field is decreasing, Lenz's Law states the induced magnetic field will oppose this change, so the induced magnetic field will also point out of the page. So to the right of this region, the right hand rule says that the electric field should point towards the top of the page, but the answer in my key is to the bottom. Am I wrong?
 
Physics news on Phys.org
The magnetic field is out of the page and decreasing - this would correspond to a south pole facing the page and being drawn away ... so the page should have an induced north pole there, because it wants to pull it back.

Which would put the current circulating anti-clockwise.
Current follows the electric field - so you seem to be right.

You could also work it from ##\nabla\times\vec E = -\frac{\partial}{\partial t}\vec B##
 
I agree with posts 1 and 2.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'
Figure 1 Overall Structure Diagram Figure 2: Top view of the piston when it is cylindrical A circular opening is created at a height of 5 meters above the water surface. Inside this opening is a sleeve-type piston with a cross-sectional area of 1 square meter. The piston is pulled to the right at a constant speed. The pulling force is(Figure 2): F = ρshg = 1000 × 1 × 5 × 10 = 50,000 N. Figure 3: Modifying the structure to incorporate a fixed internal piston When I modify the piston...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top