| Date | May 2014 | Marks available | 3 | Reference code | 14M.2.HL.TZ1.5 |
| Level | Higher level | Paper | Paper 2 | Time zone | Time zone 1 |
| Command term | Calculate, Explain, and State | Question number | 5 | Adapted from | N/A |
Question
This question is about electromagnetic induction.
A metal ring is placed in a magnetic field which is directed upwards. The magnetic flux through the ring increases over a time interval.
State and explain the direction of the current induced in the ring during this change.
The following data are available.
Resistance of ring = 3.0×10–3Ω
Initial magnetic flux = 1.2×10–5Wb
Final magnetic flux = 2.4×10–5Wb
Time interval = 2.0×10–3s
Calculate the average current induced in the ring.
Markscheme
field caused by (induced) current must be downwards;
to oppose the change that produced it;
hence the current must be clockwise;
\(\varepsilon = \left( {\frac{{\Delta \Phi }}{{\Delta t}} = } \right)\frac{{2.4 \times {{10}^{ - 5}} - 1.2 \times {{10}^{ - 5}}}}{{2.0 \times {{10}^{ - 3}}}}\) or 6.0×10-3(v);
\(I = \left( {\frac{\varepsilon }{R} = \frac{{6.0 \times {{10}^{ - 3}}}}{{3.0 \times {{10}^{ - 3}}}} = } \right)2.0\left( {\rm{A}} \right)\);
Award [2] for a bald correct answer.
Examiners report
This was generally very well answered with candidates recognizing how Lenz’s Law relates to the situation. The point that was most commonly missed was the direction of the field caused by the induced current.
As with many of the calculation questions on this paper, this was very well answered.
