CBSE Class 8 Science Exploring Forces (Class 8 NCERT New) Quiz 8

1. Which of the following correctly compares magnetic, gravitational, and electrical fields?

A All three fields require objects to be in contact to exert force B Only gravitational fields can exist in empty space C All three fields can exert forces on objects without physical contact D Electrical fields only work between magnets

2. A student is testing how the number of coils affects the strength of an electromagnet. She measures strength by counting how many paper clips the magnet can hold. Which variable should she keep constant to make this a fair test?

A The number of coils B The type of core material and battery voltage C The number of paper clips D The length of the wire only

3. A student wants to design the strongest possible electromagnet using limited materials: one iron nail, one copper nail, 50 cm of wire, and a 9V battery. Which design choice would produce the strongest electromagnet?

A Use the copper nail as the core with loosely spaced coils B Use the iron nail as the core with as many tightly wound coils as possible C Use the iron nail as the core with only 5 coils to save wire D Use no core and wrap the wire in a straight line

4. A student is asked to prove that a magnetic field exists even when two magnets are not touching. Which of the following experimental designs best supports this claim?

A Place two magnets directly on top of each other and observe attraction B Suspend a magnet on a string and bring another magnet close without touching it, observing the suspended magnet move C Rub two magnets together and observe heat D Drop a magnet on the floor and observe it bounce

5. A student claims that an electrical field does not exist unless two charged objects are touching. How would you use evidence to argue against this claim?

A Agree with the student because forces require contact B Show that a charged balloon can attract small pieces of paper without touching them, demonstrating the field exists in the space around the balloon C Show that magnets can attract metal, which proves electrical fields exist D Argue that gravitational fields are the same as electrical fields

6. Two students are debating whether gravitational force is a noncontact force. Student A says gravity only works when objects touch. Student B says gravity acts over a distance without contact. Which student is correct, and what evidence supports the correct answer?

A Student A is correct because objects must touch for any force to act B Student B is correct because the Moon orbits Earth without touching it, showing gravity acts over large distances without contact C Both students are correct because gravity works both ways D Neither student is correct because gravity is not a real force