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Comments (8)
Goh Ying Ting said
at 8:41 am on Aug 9, 2014
Hi Mr Ang, I don't really know how to approach qn 1 and qn 4 MCQ of the notes. Could you explain it to me? Thank you!
johnlittlephysics said
at 11:14 am on Aug 9, 2014
Question 1: Answer B is incorrect. Should be A.
An electron flow to the right is the same as conventional current to the left.
Apply right hand grip rule, so the field above the conductor is into the page, and below the conductor is out of the page.
johnlittlephysics said
at 11:40 pm on Aug 12, 2014
Question 4: Apply the right hand grip rule for current flowing in each coil to determine the polarity of the coils.
These show that right end of X is a South and left end of Y is a North, so both coils attract each other and move towards each other.
Siew Kah Leng said
at 9:26 am on Aug 9, 2014
Me too! I don't understand question 4 MCQ of the notes exercise questions. Thank you!
Goh Ying Ting said
at 11:24 pm on Aug 12, 2014
Hi Mr Ang, attached are questions from TYS. For this question (https://www.dropbox.com/s/82yy2u6wd8ea441/Photo%2012-8-14%2011%2033%2054%20PM.jpg), I'm not sure how to approach it to eventually get the answers in green. For this question (https://www.dropbox.com/s/1f29k5ocoh23pzy/Photo%2012-8-14%2011%2035%2028%20PM.jpg), the direction of magnetic field, I don't understand why the direction of magnetic field is the one in green. Could you explain it to me please? Thank you!
johnlittlephysics said
at 11:44 pm on Aug 12, 2014
When u paste the Dropbox link, try not to add brackets as these gets tied it the link, n cannot open the link directly.
johnlittlephysics said
at 11:51 pm on Aug 12, 2014
Q1: Use right hand grip rule (thumb point downwards along current) to determine the magnetic field (3D circular field lines) going around the straight wire carrying current.
Above the wire, magnetic field lines point to the left (compass W),
below the wire, field lines point to the right (compass E),
to left of wire, field lines point into page, and
to right of wire, field lines point out of page.
johnlittlephysics said
at 11:59 pm on Aug 12, 2014
Q2: apply right hand grip rule (fingers follow direction of current) for solenoid.
Thumb points left: direction of magnetic field line, which form a loop outside (like that of bar magnet).
Examples: magnetic field of solenoid on page 4 of topic 17 Electromagnetism notes,
and Fig. 21.5 on page 417 of textbook.
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