The variation of EMF with time for four types of generators is shown in the figures. Which amongst them can be called AC voltage?

(a)	(b)
(c)	(d)

Choose the correct option from the given ones:

In the diagram, two sinusoidal voltages of the same frequency are shown. What is the frequency and the phase relationship between the voltages?
        

An AC ammeter is used to measure the current in a circuit. When a given direct current passes through the circuit, the AC ammeter reads $6~\text A.$ When another alternating current passes through the circuit, the AC ammeter reads $8~\text A.$ Then the reading of this ammeter if DC and AC flow through the circuit simultaneously is:
1. $10 \sqrt{2}~\text A$ 
2. $14~\text A$ 
3. $10~\text A$ 
4. $15~\text A$ 

The peak value of an alternating emf; $E = E_{0}\sin\omega t$ is $10~\text V$ and its frequency is $50~\text{Hz}.$ At a time $t=\dfrac{1}{600}~\text{s},$ the instantaneous value of the emf will be:
1. $1~\text V$
2. $5\sqrt 3~\text V$
3. $5~\text V$
4. $10~\text V$

The variation of the instantaneous current $(I)$ and the instantaneous emf $(E)$ in a circuit are shown in the figure. Which of the following statements is correct?

When an alternating voltage is given as; $E = (6 \sin\omega t - 2 \cos \omega t)~\text V,$ what is its RMS value?
1. $4 \sqrt 2 ~\text V$ 
2. $2 \sqrt 5 ~\text V$ 
3. $2 \sqrt 3 ~\text V$ 
4. $4 ~\text V$