Question

An electric feild of 50kV/m is perpendicular to a magnetic field 0.25T. What is the velocity of a charge whose initial of motion is perpendicular to both fields and which passes through the fields undeflected?

3×103
3×103
m/s

2×105
2×105
m/s

4×107
4×107
m/s

5×104
5×104
m/s

Answer 1

Answer on Question #59068-Physics -Electromagnetism

An electric field of $50\mathrm{kV/m}$ is perpendicular to a magnetic field 0.25T. What is the velocity of a charge whose initial of motion is perpendicular to both fields and which passes through the fields undeflected?

$3 \times 103 \mathrm{~m/s}$

$2 \times 105 \mathrm{~m/s}$

$4 \times 107 \mathrm{~m/s}$

$5 \times 104 \mathrm{~m/s}$

Solution

Charged particles are undeflected when the electric and magnetic deflecting forces are equal (and opposite in direction).

$$qE = Bqv$$ $$v = \frac{E}{B} = \frac{50000}{0.25} = 2 \cdot 10^{5} \frac{\mathrm{m}}{\mathrm{s}}$$

Answer: $2 \times 105 \mathrm{~m/s}$.

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