All the edges of a block with parallel faces are unequal. Its longest edge is twice its shortest edge. The ratio of the maximum to minimum resistance between parallel faces is.

Answer

To solve the problem of finding the ratio of the maximum to minimum resistance between the parallel faces of a block with unequal edges, we can follow these steps:

### Step 1: Define the dimensions of the block
Let:
- \( H \) = height (shortest edge)
- \( B \) = breadth
- \( L \) = length (longest edge)

Given that the longest edge is twice the shortest edge, we can express this as:
\[ L = 2H \]

### Step 2: Write the expressions for resistance
The resistance \( R \) between two parallel faces of a block is given by the formula:
\[ R = \frac{\rho \cdot L}{A} \]
where \( \rho \) is the resistivity of the material, \( L \) is the length of the current path, and \( A \) is the cross-sectional area.

We will calculate the resistance for three different orientations:

1. **Resistance along the length \( L \)**:
- Length = \( L \)
- Area = \( B \times H \)
\[ R_L = \frac{\rho \cdot L}{B \cdot H} \]

2. **Resistance along the breadth \( B \)**:
- Length = \( B \)
- Area = \( L \times H \)
\[ R_B = \frac{\rho \cdot B}{L \cdot H} \]

3. **Resistance along the height \( H \)**:
- Length = \( H \)
- Area = \( L \times B \)
\[ R_H = \frac{\rho \cdot H}{L \cdot B} \]

### Step 3: Identify maximum and minimum resistances
From the expressions:
- \( R_L \) is the maximum resistance since \( L \) is the longest edge.
- \( R_H \) is the minimum resistance since \( H \) is the shortest edge.

### Step 4: Calculate the ratio of maximum to minimum resistance
We need to find:
\[ \frac{R_L}{R_H} \]
Substituting the expressions for \( R_L \) and \( R_H \):
\[ \frac{R_L}{R_H} = \frac{\frac{\rho \cdot L}{B \cdot H}}{\frac{\rho \cdot H}{L \cdot B}} = \frac{L^2}{H^2} \]

### Step 5: Substitute the relationship between \( L \) and \( H \)
Since we have \( L = 2H \), substituting this into the ratio gives:
\[ \frac{R_L}{R_H} = \frac{(2H)^2}{H^2} = \frac{4H^2}{H^2} = 4 \]

### Final Answer
The ratio of the maximum to minimum resistance between the parallel faces is:
\[ \boxed{4} \]