Current Electricity

Step 1: Use the Rydberg formula for hydrogen:
Step 2: For transition from to first excited state ( ):
Step 3: For transition from to ground state ( ):
Step 4: Subtract equation (1) from (2):
Step 5: Eliminate using equation (2): Substitute into Step 4 and simplify to obtain:
Step 6: Hence,

Step 1: Use the magnetic force on a current-carrying wire. The force on an element is:
Step 2: Write the differential length vector of the wire. The wire lies in the -plane with: So,
Step 3: Evaluate the cross product . Given: Using vector products:
Step 4: Integrate over the length of the wire. With :
Step 5: Find the acceleration of the wire. Mass:
Hence, the acceleration of the wire is .

Step 1: Recall the definition of conventional current. Conventional current is defined as the flow of positive charge. Step 2: Determine the direction of flow. Since positive charges are assumed to move: Step 3: Analyze the options.

(A) Direction of electron flow — incorrect
(B) Correct direction of conventional current ✔
(C) Incorrect — current has a defined direction
(D) Incorrect — current does not flow both ways
Step 4: Final conclusion. The direction of conventional current is from positive terminal to negative terminal.