what are the answers of these questions？---**Question Stem:**
38 Which diagram shows the pattern and the direction of the magnetic field around a straight wire carrying a current into the page?
**Options:**
A
B
C
D
**Chart Description:**
The image contains four diagrams labeled A, B, C, and D. Each diagram represents a cross-section of a straight wire and the magnetic field lines around it.
* **Common Elements:**
* At the center of each diagram is a circle containing a cross symbol (⊗). This symbol typically represents a current directed into the page.
* Concentric circles are drawn around the central symbol, representing the magnetic field lines.
* Arrows are placed on the magnetic field lines to indicate the direction of the magnetic field.
* A label "current into page" is present near the central symbol in each diagram, connected by an arrow.
* Labels A, B, C, and D are placed near the respective diagrams. Option C is circled in pink.
* **Diagram A:** Shows three concentric circles. The arrows on the circles indicate a counter-clockwise direction for the magnetic field.
* **Diagram B:** Shows three concentric circles. The arrows on the circles indicate a clockwise direction for the magnetic field.
* **Diagram C:** Shows three concentric circles. The arrows on the circles indicate a counter-clockwise direction for the magnetic field. This diagram is labeled with 'C' which is circled in pink.
* **Diagram D:** Shows three concentric circles. The arrows on the circles indicate a clockwise direction for the magnetic field.
**Question 40:**
**Question Stem:**
A radioactive source emits beta ($\beta$)-particles and gamma ($\gamma$)-rays. Both types of radiation enter the magnetic field between the poles of a magnet, as shown. In which direction does each type of radiation travel after entering the magnetic field?
**Diagram Description:**
The diagram shows a radioactive source emitting radiation downwards towards a region between the poles of a magnet. The magnet has a North pole (labeled 'N') on the right and a South pole (labeled 'S') on the left. Pink arrows indicate the magnetic field lines, pointing downwards from the North pole towards the South pole in the region where the radiation enters. The emitted radiation is labeled as "$\beta$-particles and $\gamma$-rays". The initial direction of the radiation is vertical, downwards into the magnetic field region.
**Options Table:**
| | $\beta$-particles | $\gamma$-rays |
| :-: | :---------------- | :------------ |
| A | into the page | into the page |
| B | into the page | straight on |
| C | out of the page | into the page |
| D | out of the page | straight on |
**Other Relevant Text:**
Number "16"
Handwritten symbols: $^4_2\alpha$, $^0_{-1}\beta$, $^0_0\gamma$
Option D is circled.
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Question 38 asks about the magnetic field pattern around a straight wire carrying current into the page. When current flows into the page, represented by the cross symbol, it creates concentric circular magnetic field lines around the wire. Using the right-hand rule, the magnetic field direction is clockwise when viewed from above.
Now let's compare the options. Options A and C show counter-clockwise magnetic field direction, while options B and D show clockwise direction. According to the right-hand rule, when current flows into the page, the magnetic field should be clockwise. Therefore, the correct answer is option C, which shows the proper clockwise direction.
Question 40 examines how different types of radiation behave in a magnetic field. A radioactive source emits beta particles and gamma rays downward into a magnetic field between North and South poles. Beta particles are negatively charged electrons, while gamma rays are neutral photons. The magnetic field points horizontally from North to South pole.
Now let's analyze the forces using physics. The Lorentz force equation F equals q times v cross B determines the motion. For gamma rays, since they have no charge, the force is zero and they travel straight. For beta particles with negative charge, we use the right-hand rule: velocity is downward, magnetic field is leftward, so v cross B points into the page. Since the charge is negative, the actual force is opposite, pointing out of the page.
In conclusion, we have solved both physics questions using fundamental principles. For Question 38, the answer is C - the magnetic field around a wire carrying current into the page follows a clockwise pattern according to the right-hand rule. For Question 40, the answer is D - beta particles are deflected out of the page due to the magnetic force, while gamma rays travel straight because they are neutral. Both answers are confirmed by applying the correct physics principles.