We have two identical fuses which are rated at 20 A. If these two are joined

Options

A. in series then their combination will act as a fuse of 10 A rating
B. in series then their combination will act as a fuse of 20 A rating
C. in parallel then their combination will act as a fuse of 40 A rating.
D. in parallel then their combination will act as a fuse of 20 A rating.

Explanation

To solve the problem of determining the effective current rating of two identical fuses rated at 20 A when connected in series and parallel, we can follow these steps:

### Step 1: Understanding Fuse Ratings
A fuse is designed to melt and break the circuit when the current exceeds its rated capacity. In this case, each fuse is rated at 20 A, meaning it will melt if the current exceeds 20 A.

**Hint:** Remember that the fuse rating indicates the maximum current it can handle before it fails.

### Step 2: Fuses in Series
When two fuses are connected in series, the same current flows through both fuses. Therefore, the effective current rating of the combination is equal to the rating of the individual fuses.

- Since both fuses are rated at 20 A, the total current that can flow through the series combination is still 20 A. If the current exceeds 20 A, either fuse will melt.

**Effective Rating in Series:** 20 A

**Hint:** In a series connection, the current is the same through all components.

### Step 3: Fuses in Parallel
When two fuses are connected in parallel, the total current flowing through the circuit is divided between the two fuses. Each fuse can carry its rated current independently.

- In this case, if one fuse carries 20 A, the other can also carry 20 A. Therefore, the total current that can flow through the parallel combination is the sum of the currents through each fuse.

**Effective Rating in Parallel:** 20 A + 20 A = 40 A

**Hint:** In a parallel connection, the total current is the sum of the currents through each branch.

### Conclusion
- **In Series:** The effective rating is 20 A.
- **In Parallel:** The effective rating is 40 A.

**Final Answer:**
- Series connection: 20 A
- Parallel connection: 40 A