12th grade electricity and magnetism

Example

Two small charged spheres carry 3 µC and 2 µC and are 0.5 m apart. What is the size of the force between them, in N? (F = k q₁ q₂ ÷ r², k = 8.99 × 10⁹ N m²/C², 1 µC = 10⁻⁶ C; give 2 decimal places)

1. F = 8.99 × 10⁹ × 3 × 10⁻⁶ × 2 × 10⁻⁶ ÷ 0.5² = 0.216
2. So the answer is: 0.22 N

Answer: 0.22 N

Example

Three resistors of 2 Ω, 15 Ω and 10 Ω are connected in series. What is the total resistance, in Ω?

1. 2 + 15 + 10 = 27
2. So the answer is: 27 Ω

Answer: 27 Ω

Example

A transformer has 500 turns on the primary coil and 2500 turns on the secondary. The input voltage is 24 V. What is the output voltage, in V? (Vp ÷ Vs = Np ÷ Ns)

1. 24 × 2500 ÷ 500 = 120
2. So the answer is: 120 V

Answer: 120 V