Question 1:
Figure 1 shows a conductor hanging from a sensitive spring balance in between a pair of Magnadur magnets.
(a) Suggest the polarity of dry cell X, Y and the polarity of magnets P, Q such that the reading of the spring balance increases when switch S is turned on.
(b) Explain why the reading of the spring balance can increase in 1(a).
(c) Suggest improvements that need to be made to further increase the reading of the spring balance.
Answer:
(a)
$$
X \text { : negative, } \quad Y \text { : positive, } P \text { : north, } \quad Q \text { : south }
$$
(b)
When switch S is turned on, current flows in the circuit from Y to X. The direction of the magnetic field from the permanent magnet is from north to south.
According to Fleming’s left-hand rule, a force acts on the conductor in the downward direction.
(c)
Increase the current by adding another dry cell in series.
Replace the permanent magnet with a stronger permanent magnet.
Figure 1 shows a conductor hanging from a sensitive spring balance in between a pair of Magnadur magnets.
(a) Suggest the polarity of dry cell X, Y and the polarity of magnets P, Q such that the reading of the spring balance increases when switch S is turned on.
(b) Explain why the reading of the spring balance can increase in 1(a).
(c) Suggest improvements that need to be made to further increase the reading of the spring balance.
Answer:
(a)
$$
X \text { : negative, } \quad Y \text { : positive, } P \text { : north, } \quad Q \text { : south }
$$(b)
When switch S is turned on, current flows in the circuit from Y to X. The direction of the magnetic field from the permanent magnet is from north to south.
According to Fleming’s left-hand rule, a force acts on the conductor in the downward direction.
(c)
Increase the current by adding another dry cell in series.
Replace the permanent magnet with a stronger permanent magnet.
Question 2:
With the aid of a labelled diagram, explain how Fleming’s left-hand rule is used to determine the direction of the force on a current-carrying conductor in a magnetic field.
Answer:
Fore finger: Direction of magnetic field
Middle finger: Direction of current
Thumb: Direction of force
With the aid of a labelled diagram, explain how Fleming’s left-hand rule is used to determine the direction of the force on a current-carrying conductor in a magnetic field.
Answer:
Fore finger: Direction of magnetic field
Middle finger: Direction of current
Thumb: Direction of force