Electricity 3 ESO

Electricity and its applications

Watch these films and answer

•  What does a battery do?
• How can we visualise potential energy?
• What happens if we use several batteries in parallel?
• What happens if we use several batteries in series?

• Look at the initial circuit and tell what is represened as: a) red balls, b)a difference of heigth c)a yellow track.
• How do they define voltage. Who provides it?
• What happens when we open an interruptor? What happens when we close it?
• Hat determines the amount of current through an electric circuit?
• What is the meaning of no current passing through a ligth bulb?
• What is the function of a properly working battery?
• How much is the potential of all points connected by wires or metal switches?
• What is the total current in a parallel circuit? And in a series circuit?
• What does Kirchoff's law refer to?
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Energy and its applications

Energy as a physical magnitude:

Energy is a crucial physical magnitude which takes time to understand:

Watch this film and answer the questions:

• What is energy
• What forms of energy exist? List them?
• Tell examples of different usages of energy during the trip. (think of objects and persons involved)
• How do they define sources of energy?
• List examples of sources of energy you see  in the film and what this source of energy is used to
• According to the video, does energy dissapear? What happens to it?

Exercises 4 ESO Dynamics Review Exam

1. A force F=(3i-4j) acts over a 2kg particle at rest during 5s. Determine: The impulse, the final linear momentum of the particle, the final speed of the particle.
   
2. If the Earth turns around the Sun in 365 days. How long does it take to Mercury? Data: dMercury-Sun=58 mill km. dEarth-Sun=150mill km
3. An hidraulic press has a minor radious of 20 cm and a bigger radious of 1m. Which force do we need to lift a 1200 kg car?Which will be the displacement to lift it 20 cm?

Ecercises 4 ESO Forces

1. Graph and order these forces by thir magnitude(-3i, 4j), (2i,8j), (-7j), (5i), (8i, -6j)
2. A R=10m ferries turns at 0.25Hz. Determine the aparent weight of a 50kg teenager when:a) he is at its bottom b)he is at its top. Draw the forces diagram
3. A bicycle rider tries to make a 15m radious looping. Which is the minimal speed he must have at the top? Draw the forces diagram
4. A horizontal spring with k=5000N/m is lengthened 10cm and then attached to a 25kg stone. If the friction quotient is 0,4 What will be the total force over the stone and the acceleration?. Draw the forces diagram

History of simple machines

Take a look at the video about simple machines (s.m) and answer

• How many parts has a simple machine got?
• What have humans created with s.m?
• What do s.m do?
• List the 6 main s.m.
• Which is the oldest s.m?
• Which is the most simple s.m.?
• How long have s.m.been being used?
• Why are simple machines called so?
• Who made the first simple machine? How old are they?
• How do we define and measure Work?
• Which s.m. is easiest to build?

Simple machines

Watch this film and answer

What is a simple machine? What is it used for?
Explain these simple machines and tell examples of them:

• Lever
• Pulley
• Inclined plane
• Wedge