Generators, Motors, Transformers

Generators generator = a machine that converts mechanical energy into electrical energy Wire loop is rotated in a magnetic field to create a current Result: a continuously changing emf

AC Generator

DC Generator

(opposite of generators) Motors (opposite of generators) motor = a machine that converts electrical energy into mechanical energy Current is supplied to a wire loop to cause it to rotate

Transformer transformer = a device that increases or decreases the emf of alternating current A transformer uses the alternating current in the primary circuit to induce an alternating current in the secondary circuit

Transformer Equation Δ 𝑉 1 =− 𝑁 1 Δ Φ 𝑀 Δ𝑡 Δ 𝑉 2 =− 𝑁 2 Δ Φ 𝑀 Δ𝑡 Δ 𝑉 1 =− 𝑁 1 Δ Φ 𝑀 Δ𝑡 Δ 𝑉 2 =− 𝑁 2 Δ Φ 𝑀 Δ𝑡 Δ 𝑉 2 = 𝑁 2 𝑁 1 Δ 𝑉 1 induced emf in secondary=( # turns in secondary # turns in primary )×applied emf in primary Step-up transformer: N2>N1 Step-down transformer: N2<N1 A step-up transformer can change 10 V to 100 V, but not without a cost. The power stays the same, so current in the secondary will be less

Practice A step-up transformer is used on a 120 V line to provide a potential difference of 2400 V. If the primary has 75 turns, how many turns must the secondary have?

Practice A step-down transformer has 525 turns in its secondary and 12,500 turns in its primary. If the potential difference across the primary is 3,510 V, what is the potential difference across the secondary?