Question

A device which helps to lift heavy loads or speed up the motion or change the direction of force in the desired direction.
A. Machine
B. Magnets
C. Motor
D. All

Answer 1

Hint: The direction of the force can be changed by reversing the direction of the current. This causes the reverse on the magnetic field through the wire. This reverses the force in the desired location. There are a variety of machines, magnets or motors which help to lift objects of small weight. While there are few machines, motors or magnets which can also help to lift heavy loads.

Complete answer:
There are various machines which help to lift heavy loads. To lift those heavy loads, machines have levers. Generally, machines which belong to second class levers are used to lift heavy loads. Examples for such machines include pulley, crane, crowbar, etc. These devices also change the direction of the force in the desired direction or can also speed up the motion.
Magnets help to make a tight seal on the doors of refrigerators and freezers. Magnets are used in appliances which are used in house, business or medical industry. Magnets are used to transform mechanical energy to electric energy. Electromagnets are used to lift heavy loads. Changing the direction of the magnetic field can also change the direction of the force.
Motors are used to transform electrical energy to mechanical energy. Motors can be used to lift an object of 100 kg. By inverting the polarity of applied voltage, the direction of motors can be turned in either direction. Hence, the force can actually be created in either direction using motors.
Hence, machines, motors and magnets help to load or speed up the motion or change the direction of force in the desired direction.

So, the correct answer is “Option D”.

Note:
A gearbox is a machine which is typically used as a speed reducer whereas a lever is used as a force increaser. Stepper motors can be used to lift an object which weighs 100 kg. Typically, electromagnets are used to lift electromagnets and not permanent magnets because it does not lose its magnetic property. Magnets are fixed inside the machines which helps to lift heavy objects as well as to speed up the motion.