The velocity of certain ions that pass undeflected through crossed electric field E = 7.7 kV/m and magnetic field B = 0.14 T is (1) 18 km/s (2) 77 km/s (3) 55 km/s (4) 1078 km/s

18 km/s
77 km/s
55 km/s
1078 km/s

Correct answer: 55 km/s

Solution

The ions pass undeflected when the electric force equals the magnetic force, which can be calculated using the formula v = E/B. Substituting the given values (E = 7.7 kV/m = 7700 V/m and B = 0.14 T) results in a velocity of 55 km/s, confirming that this is the correct option.

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