A bulb is connected first with `DC` and the then `AC` of same voltage then it will shine brightly with

Options

A. `AC`
B. `DC`
C. Brightness will be in ratio `1//1.4`
D. Equally with both

Explanation

To determine whether the bulb shines more brightly with AC or DC when both are at the same voltage, we can analyze the power dissipated by the bulb in both scenarios.

### Step-by-Step Solution:

1. **Understanding Brightness and Power**:
- Brightness of a bulb is directly related to the power it dissipates. The power \( P \) dissipated by a resistive load (like a bulb) can be expressed as:
\[ P = \frac{V^2}{R} \]
where \( V \) is the voltage across the bulb and \( R \) is the resistance of the bulb.

2. **Voltage for DC and AC**:
- In the problem, it is stated that the bulb is connected first to a DC source and then to an AC source, both having the same voltage \( V \).

3. **Power Calculation for DC**:
- For DC, the power can be calculated using the formula:
\[ P_{DC} = \frac{V^2}{R} \]
Here, \( V \) is the constant voltage of the DC source.

4. **Power Calculation for AC**:
- For AC, the situation is a bit different because the voltage is not constant; it varies with time. However, when we talk about AC voltage, we often refer to the RMS (Root Mean Square) voltage, which is given by:
\[ V_{rms} = \frac{V_{peak}}{\sqrt{2}} \]
- If the AC voltage is equivalent to the same DC voltage in terms of power, we can use the RMS value directly in the power formula:
\[ P_{AC} = \frac{V_{rms}^2}{R} \]
- Since we are given that the AC voltage is the same as the DC voltage, we can consider \( V_{rms} = V \).

5. **Comparing Power for AC and DC**:
- Since both the DC and AC voltages are the same, we have:
\[ P_{AC} = \frac{V^2}{R} \]
- Thus, the power dissipated in both cases is equal:
\[ P_{DC} = P_{AC} \]

6. **Conclusion**:
- Since the power (and thus brightness) is the same for both AC and DC when the voltage is the same, we conclude that the bulb will shine equally brightly in both cases.

### Final Answer:
The bulb will shine equally brightly with both AC and DC.