Explanation:
We know that a changing magnetic field induces a current in a conductor. For that reason a generator basically consist an element that produces a magnetic field that changes over time and a conductor where the current will be induced.
This element that produces a magnetic field can be one of the following:
- A permanent magnet: Which is basically like a regular magnet. The magnetic field that a permanent magnet produces does not change over time, we need a motor or any other external force to move the axis of the generator and cause the magnetic field to change.
- An electro-magnet. Which is basically a DC current flowing through a conductor. Basically, when current flows through a conductor it behaves exactly like a magnet. So what we commonly do, is to connect a conductor to a DC battery, and it will create a magnetic field.
Like we are using a DC battery to create a magnetic field, then the magnetic field won't change over time either. So we still need an external force to move the axis of the generator to produce AC electricity.
Answer:
Explanation:
Electric flux is defined as the flow of electric field intensity through a given surface.
Mathematically:

where:
E = electric field
A = area
θ = angle between the area vector and the electric field
Electric flux through the surface of a sphere will be uniform throughout the surface area due to a charge at the center of the sphere. The distance of the surface from the center is always at a constant distance of radius of the sphere.
Electric flux through the surface of a cube will be varying as the surface area is at a varying distance from the center of the cube. The distance of the surface from the center is not at a uniform distance from the center of the cube and so the projection of solid angle changes.
The given problem can be exemplified in the following diagram:
Since there is no friction or any other external force, the only force acting in the direction of the movement is the component of the weight of the block, therefore, applying Newton's second law:

Replacing the values:

We may cancel out the mass:

Using the gravity constant as 9.8 meters per square second:

Solving the operations:

Therefore, the acceleration is 6.3 meters per square second.
The answer to this is D. Green.
Answer:
Mumbai
Explanation:
Because Mumbai is a coastal city
due to high humidity,vigorous rusting damages all the iron structures
∴ rusting is a major problem in Mumbai