# AP Inter 2nd Year Physics Notes Chapter 10 Alternating Current

Students can go through AP Inter 2nd Year Physics Notes 10th Lesson Alternating Current will help students in revising the entire concepts quickly.

## AP Inter 2nd Year Physics Notes 10th Lesson Alternating Current

→Alternating current means the current whose magnitude changes with time and direction reverses periodically.

→ Average value (or) Mean value of A.C is equal to that steady current which when passed of A.C will send the same amount of charge by alternating current in the same time through the same circuit.

→ R.M.S value of A.C is defined as that steady current which produces the same amount of heat in a conductor in a certain time interval as is produced by the A.C in the same conductor during the time period (T).

→ When A.C is passed through a resistor, the voltage is in phase with the current.

→ When A.C is passed through an inductor, the voltage leads the current by a phase angle $$\frac{\pi}{2}$$ (or) 90°

→ When A.C is passed through a capacitor the voltage lags behind the current by a phase angle $$\frac{\pi}{2}$$ (or) 90° → The resistance offered by an inductor to a.c is called inductive reactance.

→ The resistance offered by a capacitor to a.c is called capacitive reactance.

→ Power is dissipated only due to ohmic resistance R in an a.c circuit.

→ Power factor is one for purely capacitive (or) inductive circuit.

→ A transformer is based on the principle of mutual inductance.

→ Transformer works on a.c and not on d.c.

→ Transformer is a device for converting alternating voltage (at high current) to high voltage (at low current) and viceversa.

→ Instataneous power is defined as the product of the instantaneous voltage and instantaneous current. → Q- factor is defined as the ratio of the voltage drop across inductor (or) capacitor to the applied voltage.

→ Sharpness of resonance is the ratio of resonant angular frequency to the bandwidth of the circuit.

→ Choke coil is used to control a.c with out much loss of electric power.

→ In generators and motors, the roles of input and output are reversed.

→ In a motor, electric energy is the input and mechanical energy is the output.

→ In a generator, mechnical energy is the input and electrical energy is the output.

Formulae

→ Alternating current and voltage
i = im sin ωt and V = Vm sin ωt

→ Vrms = $$\frac{\mathrm{V}_{\mathrm{m}}}{\sqrt{2}}$$ and irms = $$\frac{\mathrm{i}_{\mathrm{m}}}{\sqrt{2}}$$

→ Inductive reactance (XL) = ωL

→ Capacitive reactance (XC) = $$\frac{1}{\omega C}$$ → Impedence (Z) = $$\sqrt{\mathrm{R}^2+\left(\frac{1}{\omega \mathrm{C}}-\omega \mathrm{L}\right)^2}$$
= $$\sqrt{\mathrm{R}^2+\left(\mathrm{X}_{\mathrm{C}}-\mathrm{X}_{\mathrm{L}}\right)^2}$$

→ Φ = tan-1 $$\left(\frac{\frac{1}{\omega C}-\omega L}{R}\right)$$ = tan-1 $$\left[\frac{\mathrm{X}_{\mathrm{C}}-\mathrm{X}_{\mathrm{L}}}{\mathrm{R}}\right]$$

→ f0 = $$\frac{1}{2 \pi \sqrt{L C}}$$

→ Q-factor = $$\frac{\omega_0 L}{R}=\frac{1}{\omega_0 C R}$$

→ Average power (P) = Vrms × Irms × cos Φ

→ Transformer ratio = $$\frac{N_s}{N_p}=\frac{V_s}{V_p}$$