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UNIT 3 BAT REVIEW Electromagnetic Force

UNIT 3 BAT REVIEW Electromagnetic Force. March 8, 2018. Forces. A force is a push or a pull It doesn’t matter if you push or pull Forces are measured in units called Newtons You measure force with an instrument called a spring scale. Why Are Forces Important?.

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UNIT 3 BAT REVIEW Electromagnetic Force

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  1. UNIT 3 BAT REVIEWElectromagnetic Force March 8, 2018

  2. Forces • A force is a push or a pull • It doesn’t matter if you push or pull • Forces are measured in units called Newtons • You measure force with an instrument called a spring scale

  3. Why Are Forces Important? • In order for something to change motion, you need to apply a force. • If you want something to start moving, you need a force • If you want something to stop moving, you need a force in the opposite direction • If you want something to speed up, slow down, or turn, you need a force!

  4. Examples of Forces • Contact Force – Pushing something • Gravity – Pulls down on you • Magnetic Force – We’ll get to that later • Normal Force – The ground pushing back up on you when you sit or stand. • Friction – See next slide

  5. Friction • Friction is the force two objects create when they push against each other. • Friction always acts in a direction opposite of motion. It can keep you from moving or slow you down • You can reduce friction by Using Wheels (Rolling Friction) Going on Liquid (Fluid Friction) Floating on Air (Also Fluid Friction)

  6. Adding Forces (Net Force) • If two forces are in the same direction, they add together • If two forces are in opposite directions, they cancel out • If two forces add up to 0N, we say that they are in equilibrium, and motion does not change

  7. Newton’s 1st Law of Motion • Newton’s 1st Law of Motion (Inertia) – An object in motion stays in motion in a straight line, and an object at rest stays at rest unless acted upon by an unbalanced force.

  8. Newton’s 2nd Law of Motion • Newton’s 2nd Law of Motion – Force equals mass times acceleration • More force means more acceleration • More mass means less acceleration

  9. Newton’s 3rd Law of Motion • Newton’s 3rd Law of Motion – For every action, there is an equal and opposite reaction • If I push the door with 200 N of force, the door pushes back on me with 200 N • So we’re in equilibrium and the door doesn’t move

  10. Magnetism • A permanent magnet is an object that always exerts a magnetic force • When an object that is ferromagnetic (contains iron, cobalt, or nickel) gets close to a permanent magnet, it becomes a temporary magnet. • So the permanent magnet induces magnetism in the temporary magnet

  11. Rules of Magnetism • Every magnet has two poles – a north pole and a south pole • Opposite poles (N/S) attract • Like poles (N/N, S/S) repel • Compasses work because the Earth is a giant magnet

  12. Magnetic Fields • A magnet has a magnetic field. Anything ferromagnetic in the field has magnetism induced in it. • Magnetic fields go on forever but get weaker with distance • Magnetic fields can extend through objects like paper. • Magnetic fields are strongest at the poles and weakest in the middle

  13. Electricity • Electricity flows in a closed circuit. This is a path that starts at a power source and flows back uninterrupted to the other side of the source. • With batteries, electricity flows from the negative terminal to the positive terminal • Some things that can open circuits are flowing from plus to plus, or an open switch, or flowing to the same part of a component

  14. Electromagnets • When electricity flows through a wire, it creates a magnetic field. • If you coil this wire around a ferromagnetic core enough times, the field is strong enough to have a visible effect – we call this an electromagnet • Electromagnets are useful because they can turn on and off

  15. Variables That Can Affect Electromagnets • For an electromagnet to work, the coiled wire needs to be insulated • The more coils you wrap around the core, the stronger the magnetic field • The tighter you wrap the coils, the stronger the magnetic field • The thicker the wire, the stronger the magnetic field. • The more voltage (battery power) you have, the stronger the magnetic field

  16. Motors • A motor converts electrical energy into kinetic energy • It works because it has two wires powering three electromagnets • Since only two electromagnets are on, only those two go to the permanent magnets • But as the shaft moves, one electromagnet turns off and another turns on and it goes to the permanent magnet. • As the shaft keeps turning, this process keeps going

  17. Generators • A generator is like a motor, except that it works in reverse • So a generator converts kinetic energy into electrical energy. • Power plants use large generators powered by turbines – the different kinds use different methods to get the turbine to turn.

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