Hans Christian Oersted, in 1820, observed that when an electric current flows through a conductor, a nearby compass needle deflects. This experiment showed a link between electricity and magnetism.
(a) What conclusion did Oersted draw from his experiment? (1 Mark)
(b) How can the direction of the magnetic field around a straight conductor be determined? (2 Marks)
(c) What happens to the magnetic field strength if the current in the conductor is increased? (1 Mark)
OR
(c) What happens to the direction of the magnetic field when the current direction is reversed? (1 Mark)
Ans:
(a) Oersted concluded that a current-carrying conductor produces a magnetic field around it.
(b) The Right-Hand Thumb Rule is used:
- Hold the conductor in your right hand with thumb pointing in the direction of current.
- The curled fingers show the direction of the magnetic field.
(c) If current increases, the magnetic field strength also increases.
OR
(c) If current direction is reversed, the magnetic field also reverses.
Q2: Read the source below and answer the questions that follow:
A student set up an experiment using a straight wire, a battery, and a compass. When current was passed, the compass needle deflected.
(a) What shape do magnetic field lines form around a straight conductor? (1 Mark)
(b) How does the strength of the magnetic field change with distance from the wire? (2 Marks)
(c) What happens to the field lines when the current is doubled? (1 Mark)
OR
(c) How can the direction of the magnetic field be reversed? (1 Mark)
Ans:
(a) The magnetic field lines form concentric circles around the conductor.
(b)
- The field is stronger near the wire and weaker farther away.
- Larger circles represent weaker fields as distance increases.
(c) If current is doubled, the magnetic field strength also doubles.
OR
(c) The current direction must be reversed to reverse the magnetic field direction.
Q3: Read the source below and answer the questions that follow:
In an experiment, a circular wire loop was connected to a battery, and iron filings were sprinkled around it. The filings aligned in circular patterns.
(a) How does the magnetic field behave at the center of a current-carrying circular loop? (1 Mark)
(b) What factors affect the strength of the magnetic field in a circular loop? (2 Marks)
(c) What happens to the field strength if the number of turns in the loop is increased? (1 Mark)
OR
(c) How does increasing the radius of the loop affect the magnetic field? (1 Mark)
Ans:
(a) At the center of the loop, the field lines are nearly straight and strong.
(b) The magnetic field depends on:
- Current in the loop (higher current → stronger field).
- Number of turns in the coil (more turns → stronger field).
(c) More turns increase the field strength, as each turn adds to the total effect.
OR
(c) A larger loop radius reduces the field strength at the center.
Q4: Read the source below and answer the questions that follow:
A scientist demonstrated that a current-carrying solenoid behaves like a bar magnet. He placed a compass near the solenoid’s ends and observed north and south poles.
(a) What is a solenoid? (1 Mark)
(b) How does a solenoid produce a uniform magnetic field? (2 Marks)
(c) How can a solenoid be used to create a strong electromagnet? (1 Mark)
OR
(c) How does a solenoid’s field compare to that of a bar magnet? (1 Mark)
Ans:
(a) A solenoid is a coil of insulated wire wound in a cylindrical shape.
(b) The magnetic field lines inside a solenoid are parallel, indicating a uniform field similar to a bar magnet.
(c) A strong electromagnet can be made by:
- Increasing the current.
- Increasing the number of turns in the coil.
- Using a soft iron core.
OR
(c) A solenoid’s field is similar to a bar magnet’s, with north and south poles at its ends.
Q5: Read the source below and answer the questions that follow:
In households, fuses and circuit breakers prevent damage caused by short circuits or overloading.
(a) What is the purpose of a fuse in an electric circuit? (1 Mark)
(b) How does a fuse protect electrical appliances? (2 Marks)
(c) Why should high-power appliances be connected separately in a house? (1 Mark)
OR
(c) What is the function of an earth wire in a household circuit? (1 Mark)
Ans:
(a) A fuse prevents excessive current flow, protecting the circuit.
(b) Purpose of fuse :
- A fuse melts when current exceeds a limit, breaking the circuit.
- This prevents overheating and fire hazards.
(c) High-power appliances draw more current, and separate circuits prevent overloading.
OR
(c) An earth wire provides a safe path for excess current, preventing electric shocks.
Q6: Read the source below and answer the questions that follow:
During a science fair, a student demonstrated that when a current flows through a conductor placed in a magnetic field, the conductor experiences a force and moves. This is the working principle of many electrical devices, including electric motors.
(a) What happens when a current-carrying conductor is placed in a magnetic field? (1 Mark)
(b) Explain how the direction of force on the conductor can be determined. (2 Marks)
(c) What happens if the direction of the current is reversed? (1 Mark)
OR
(c) Why does a charged particle moving in a magnetic field experience a force? (1 Mark)
Ans:
(a) A force acts on the conductor, causing it to move in a direction perpendicular to both the current and the magnetic field.
(b) The direction of force can be determined using Fleming’s Left-Hand Rule:
- Forefinger → Direction of magnetic field
- Middle finger → Direction of current
- Thumb → Direction of force/motion
(c) If the current direction is reversed, the force direction is also reversed, causing the conductor to move in the opposite direction.
OR
(c) A moving charged particle creates a current, which interacts with the magnetic field, experiencing a force perpendicular to both its velocity and the field.
