Answer:
1.True
2.True
3.True
4.True
5.False
Explanation:
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets.
Magnetism is light: Why do magnets stick? Magnets attract each other because they exchange photons, or the particles that make up light. But unlike the photons streaming out of a desk lamp or reflecting off of everything you see around you, these photons are virtual, and your eyes (or any particle detector) can't "see" them. They can, however, exchange momentum, and this is why they stick to things or repel them. When a kid throws a dodge ball, they're exchanging momentum with the ball, and the thrower feels a slight push back. Meanwhile the target person feels the force of the ball, and (maybe) gets knocked over — they are "repelled" from the thrower. With photons, the process can also happen in reverse, as though one kid reached out and grabbed the ball while the other was still hanging on to it, which would look like an attractive force.
Magnetism is relativistic: That's right — whenever you turn on an electromagnet and stick it to a fridge, you are demonstrating relativity. Why? According to the theory of special relativity, the distance along the direction of motion gets shorter — that is, a fast-moving car would look squished, even though the person in the car wouldn't notice. That person would see everything around him or her as squished in the direction in which the individual was traveling.
This has consequences for charged particles in wires. Ordinarily, the negatively charged electrons and positively charged protons in a wire cancel each other out. But when current moves through a wire, the electrons are moving. From the point of view of any stationary charged particle outside the wire, the distance between electrons gets smaller. That means it looks like there are more electrons than protons in a given space — all of a sudden there's a net negative charge. Put any positively charged particle (or wire) next to the wire with current in it, and you feel a magnetic force of attraction. Put a negatively charged particle near it and it will repel — and this is why if you run the current in opposite directions through two wires, they will attract each other, and if the current is running in the same direction, they will repel.
A similar thing happens when a charged particle moves through a magnetic field, say, near a (permanent) bar magnet. The particle experiences force. But according to the theory of relativity, you can't say that the particle is moving and the magnet isn't. From the point of view of the particle, the bar magnet is moving. Maxwell's equations, which describe electromagnetic waves and forces, show that you'd see different forces, depending on which reference frame you choose. For a stationary observer it looks like a magnetic force pushing or pulling on the particle, and for a moving one it's an electrostatic force. This problem was a major piece of Einstein's development of special relativity, which accounted for the discrepancy.
