A pinhole camera<span> is a simple </span>camera<span> without a lens but with a tiny aperture, a</span>pinhole<span> – effectively a light-proof box with a small hole in one side. Light from a scene passes through the aperture and projects an inverted image on the opposite side of the box, which is known as the </span>camera<span> obscura effect.</span>
Answer:
1) The strength of the electromagnet increases → Place a magnetic core inside the coil of wire
2) The electromagnet turns off → Turn off the battery supply
3) The poles of the electromagnet reverse → Change the direction in which the current flows
Explanation:
when current passes through a coil it behaves a an electromagnet.
Magnetic field strength is given by
B = μ N I
N is no of turns and
I is the current through coil
μ is permeability of the medium or core in the coil.
1). Magnetic core increase permeability μ so it will strengthen magnetic field:
B = <u>μ</u> N I
2). When the battery turns off current becomes zeroi.e I=0
So B = μ N * 0
⇒ B = 0
so electromagnet turns off
3). Direction of magnetic field can be determine by right hand rule, i.e curl the fingers in the direction of current, thumb will point in the direction of north pole.
so changing current direction will change direction of magnetic field.
Answer:
C) Contact
Explanation:
The magnet requires almost direct <u>contact</u> with the fridge to start its magnetic properties.
For help with this answer, we look to Newton's second law of motion:
Force = (mass) x (acceleration)
Since the question seems to focus on acceleration, let's get
'acceleration' all alone on one side of the equation, so we can
really see what's going on.
Here's the equation again:
Force = (mass) x (acceleration)
Divide each side by 'mass',
and we have: Acceleration = (force) / (mass) .
Now the answer jumps out at us: The rate of acceleration of an object
is determined by the object's mass and by the strength of the net force
acting on the object.
