The instantaneous power of a 1-phase series circuit supplying an R-L load from a sinusoidal voltage source has in each cycle a) negative twice, zero four times. This means that the power alternates between negative values and zero values during each cycle. Let's break down the explanation into the following headings:

1. Understanding the R-L Circuit
2. Instantaneous Power in an R-L Circuit
3. Analysis of the Sinusoidal Voltage Source
4. Instantaneous Power in Each Cycle
5. Conclusion

1. Understanding the R-L Circuit:
- In a 1-phase series circuit with an R-L load, the load consists of a resistor (R) and an inductor (L) connected in series.
- The resistor dissipates power in the form of heat, while the inductor stores and releases energy in the form of a magnetic field.

2. Instantaneous Power in an R-L Circuit:
- The instantaneous power in an R-L circuit can be calculated using the formula P(t) = VIcos(θ), where P(t) is the power at time t, V is the voltage, I is the current, and θ is the phase angle between the voltage and current waveforms.
- In an R-L circuit, the current lags behind the voltage due to the inductive nature of the load. This lag is represented by the phase angle θ.

3. Analysis of the Sinusoidal Voltage Source:
- A sinusoidal voltage source produces a waveform that varies sinusoidally with time.
- The voltage waveform can be represented as V(t) = Vm sin(ωt), where Vm is the peak voltage, ω is the angular frequency, and t is the time.

4. Instantaneous Power in Each Cycle:
- During each cycle of the sinusoidal voltage source, the instantaneous power will go through different phases.
- At the beginning of the cycle, when the voltage is positive, the current will start to flow through the circuit. As the current increases, the power will also increase and become positive.
- As the voltage reaches its peak, the current will reach its peak with a certain phase lag. At this point, the power will be at its maximum positive value.
- As the voltage starts to decrease, the current will also start to decrease, causing the power to decrease and eventually become zero.
- When the voltage crosses zero and becomes negative, the current will continue to decrease, but in the opposite direction. This will result in negative power.
- As the current reaches its negative peak, the power will be at its maximum negative value.
- Finally, as the voltage becomes positive again, the current will start to increase in the opposite direction, causing the power to decrease and eventually become zero.

5. Conclusion:
In each cycle of a 1-phase series circuit supplying an R-L load from a sinusoidal voltage source, the instantaneous power has a pattern of being negative twice and zero four times. This pattern occurs due to the phase difference between the voltage and current waveforms in an R-L circuit.