Physics Self-Test - Page 10
68- If the flow of electric current is parallel to the magnetic field, the force will be _________
- a) Zero
- b) Infinity
- c) Maximum
- d) Half the original value
Explanation: The magnetic force on a moving charge or conductor depends on the cross-product vector calculation ($F = I L \times B$). When parallel ($\theta = 0^\circ$), the sine factor drops to zero, yielding no net force.
69- According to Lorentz force, the ratio of magnetic force to electric force on a charged particle getting undeflected in a field is?
Explanation: For a particle to traverse cross-fields completely undeflected, the upward electrical force must balance the downward magnetic vector component identically ($F_E = F_M$). Consequently, their absolute ratio equals exactly 1.
70- The H quantity is analogous to which component in the following?
71- Given the magnetic field is 2.4 units. Find the flux density in air (in 10^-6 order).
72- Find the electric field when the magnetic field is given by 2sin t in air.
- a) 8π × 10¹» cos t
- b) 4π × 10¹» sin t
- c) -8π × 10¹» cos t
- d) -4π × 10¹» sin t
H = 2sin t. We get B = μ₀H = 4π × 10¹» × 2sin t = 8π×10¹» sin t.
To get E, integrate B with respect to time, we get 8π×10¹» cos t.
73- Find the magnetic field intensity due to a solenoid of length 12cm having 30 turns and current of 1.5A.
- a) 250
- b) 325
- c) 175
- d) 375
74- Find the magnetic field intensity at the radius of 6cm of a coaxial cable with inner and outer radii are 1.5cm and 4cm respectively. The current flowing is 2A.
- a) 2.73
- b) 3.5
- c) 0
- d) 1.25
Explanation: The inner radius is 1.5cm and the outer radius is 4cm. It is clear that the magnetic field intensity needs to be calculated outside of the conductor
75- Calculate the magnetic field intensity due to a toroid of turns 50, current 2A and radius 159mm.
- a) 50
- b) 75
- c) 100
- d) 200
Explanation: Using the toroid system evaluation formula: $H = \frac{N \cdot I}{2\pi r} = \frac{50 \cdot 2}{2 \cdot \pi \cdot 0.159} \approx \frac{100}{0.999} \approx 100\text{ units}$.