Which of the following statements is/are true for a current carrying straight conductor?
(i) The magnetic field lines are concentric circles with conductor at the centre.
(ii) The strength of the magnetic field increases as we move away from the conductor:
(iii) The direction of magnetic field can be determined using right hand thumb rule.

Correct option is B

The correct answer is (B) Both (i) and (iii).

Statement (i): The magnetic field lines are concentric circles with the conductor at the center. This is true.
Around a current-carrying straight conductor, the magnetic field forms concentric circles with the conductor at the center, as described by Ampere's law.

Statement (ii): The strength of the magnetic field increases as we move away from the conductor. This is false.
The magnetic field strength decreases as we move away from the conductor. According to the formula $$B \propto \frac{1}{r}$$, where r is the distance from the conductor, the field weakens with distance.

Statement (iii): The direction of the magnetic field can be determined using the right-hand thumb rule. This is true.
The right-hand thumb rule states that if the thumb of the right hand points in the direction of the current, the curled fingers around the conductor give the direction of the magnetic field lines.