Given:
- Rotor radius = 1.3 cm
- Magnetic thickness = 0.25 cm
- Year gabling = 0.05 cm

To find: Magnetic flux density

Formula: Magnetic flux density (B) = Magnetic flux (Φ) / (Cross-sectional area of rotor)

1. Calculate the cross-sectional area of the rotor
- The cross-sectional area of the rotor can be calculated as the difference between the area of the outer circle and the area of the inner circle.
- Outer circle area = π * (radius + magnetic thickness)^2
= π * (1.3 + 0.25)^2
= 6.76 cm^2
- Inner circle area = π * radius^2
= π * 1.3^2
= 5.31 cm^2
- Cross-sectional area = Outer circle area - Inner circle area - Year gabling
= 6.76 - 5.31 - 0.05
= 1.4 cm^2

2. Calculate the magnetic flux
- The magnetic flux can be calculated using the formula Φ = B * A, where A is the cross-sectional area and B is the magnetic flux density.
- Rearranging the formula, we get B = Φ / A
- Assume that the magnetic flux φ is equal to the product of the magnetic field strength (H) and the length of the rotor (l).
- H is not given, so we assume a typical value of 1000 A/m.
- The length of the rotor can be calculated as the product of the circumference and the number of magnetic poles (p).
- The circumference can be calculated as 2 * π * radius = 8.17 cm.
- The number of magnetic poles is not given, so we assume a typical value of 4.
- Therefore, l = circumference * p = 8.17 * 4 = 32.68 cm.
- Φ = H * l = 1000 * 32.68 = 32680 Wb
- B = Φ / A = 32680 / 1.4 = 23342.86 G
- Converting G to T, we get B = 2.3343 T

Answer: The magnetic flux density in the motor is 2.3343 T, which is approximately equal to option B) 1.03 T.

D