IB myp 4-5 physics – Practice Questions- All Topics
Topic :Electromagnetism-Electric Fields
Topic :Electromagnetism– Weightage : 21 %
All Questions for Topic : Electric Fields,Static Electricity ,Magnetism,Magnetic Fields,Current,Power,Voltage,Electric Circuits,Electric and Magnetic Fields,Electromagnetic forces and induction
How does lightning occur?
Inside a thunder cloud, ice crystals collide and transfer charge between themselves. Even though the ice crystals are made of the same material, heavier crystals tend to acquire a negative charge
while smaller ice crystals become positively charged. The larger, negatively charged ice crystals sink to the bottom of the thunder cloud and the positively charged ice crystals float to the top.
When the bottom of the thunder cloud has enough charge, it starts to induce a positive charge in the ground underneath it. Atoms in the air experience opposite forces on them as the electrons are pulled towards the ground, while the protons in the atomic nucleus are pulled upwards. When these forces are large enough to pull an electron off the atom, a spark occurs. On this large scale, the spark is a bolt of lightning.
Question:
When lightning strikes, the bottom of the thunder cloud is negatively charged. Determine the direction in which the electrons will travel.
▶️Answer/Explanation
Ans: From the cloud to the ground (negative to positive).
Question:
Explain why the electric field will pull the electrons and the nuclei of air molecules in different directions.
▶️Answer/Explanation
Ans: Electrons are negatively charged and nuclei are positively charged; the negative electrons are attracted downwards, towards the positively charged ground; the positive nuclei are attracted upwards, towards the negatively charged ground.
Question:
The presence of the negatively charged thunder cloud causes the ground to acquire a positive charge by a process caused induction. Explain how this works.
▶️Answer/Explanation
Ans: The electrons in the ground are able to move a little; the nuclei of the atoms are not able to move; opposite charges repel, like charges attract; when the negatively charged cloud is close to the ground, the electrons in the ground are repelled as they are also negatively charged; ground is left with fewer electrons and so has a positive charge.