Practice free Alternating Current (Physics) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
The phase angle $\phi$ for a series RLC circuit, which determines the phase difference between the source voltage and the current, can be determined using the formula:
The NCERT text (Eq. 7.27) states, '$\tan\phi = \frac{X_C - X_L}{R}$'.
A phasor is defined as a vector that rotates about the origin. What does its angular speed represent?
The NCERT text defines a phasor as 'a vector which rotates about the origin with angular speed $\omega$'.
In a series RLC circuit, the current phasor I is commonly drawn horizontally as a reference. In this representation, where would the voltage phasor across the resistor (VR) be located?
The NCERT notes that in an RLC circuit, 'VR is parallel to I'. This means they are in phase and drawn in the same direction on a phasor diagram.
If the voltage across an AC source is given by $v = v_m \sin(\omega t)$ and the current in a particular circuit element is $i = i_m \sin(\omega t + \pi/2)$, which type of element is predominant in determining the phase relationship?
The current waveform $i = i_m \sin(\omega t + \pi/2)$ indicates that the current leads the voltage by $\pi/2$. This phase relationship is characteristic of a purely capacitive circuit, where the current through the capacitor is $\pi/2$ ahead of the applied voltage.
In a series RLC circuit, the individual voltage phasors V_L, V_R, and V_C combine to form the total voltage phasor V. If V_C and V_L are always along the same line and in opposite directions, what is the magnitude of their combined phasor $(V_C + V_L)$?
The NCERT text states, 'Since VC and VL are always along the same line and in opposite directions, they can be combined into a single phasor (VC + VL) which has a magnitude $|v_{Cm} – v_{Lm}|$.' This corresponds to $|V_C - V_L|$ for the RMS or peak voltage magnitudes.
The analysis of an AC circuit is simplified by using phasor diagrams because:
The NCERT text highlights this benefit: 'The analysis of an ac circuit is facilitated by the use of a phasor diagram.' And further explains, 'The rotating vectors that represent harmonically varying scalar quantities are introduced only to provide us with a simple way of adding these quantities using a rule that we already know as the law of vector addition.'
The RMS value of an alternating current (AC) is defined as the equivalent direct current (DC) that would produce the same:
According to the provided text, 'In fact, the I or rms current is the equivalent dc current that would produce the same average power loss as the alternating current.' This highlights the fundamental definition and significance of RMS current in terms of power dissipation.
What is the relationship between the RMS current ($I$) and the peak current ($I_m$) for a sinusoidal AC current?
The text states: '$I = \frac{I_m}{\sqrt{2}} = 0.707 I_m$'. This is the standard definition of the RMS value for a sinusoidal alternating current.
The household line voltage in India is typically 220 V. This value represents the:
The context explicitly mentions, 'It is customary to measure and specify rms values for ac quantities. For example, the household line voltage of 220 V is an rms value'. This confirms that such general ratings refer to RMS values.
If the RMS voltage of a household supply is 220 V, what is the peak voltage ($V_m$) of the source?
The text provides the calculation: '$V_m = \sqrt{2} V = (1.414)(220 V) = 311 V'$. This shows how to convert from RMS voltage to peak voltage.
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