Electrical Instruments

Step 1: Understand LED characteristics.
LEDs (Light Emitting Diodes) have several key characteristics, such as fast action, low operational voltage, and long life.
They turn on instantly and do not require warm-up time, unlike some traditional lighting sources.
Step 2: Identify the incorrect option.
LEDs have a very fast response time, which means they don’t require a high warm-up time.
Hence, option (b) is the correct answer.

Step 1: Understand resistor color codes.
Resistor color codes are used to indicate the value and tolerance of resistors.
These codes were originally developed to standardize the identification process.
Step 2: Identify the organizations involved.
Both the Radio Manufacturers Association (RMA) and the International Organization for Standardization (ISO) were involved in developing resistor color codes.
The EIA also contributed, but the key organizations are RMA and ISO.

Step 1: Understand the setup.
The total emf of 36 cells, each with an emf of 4V, when all are connected in series, is: However, the outside emf is given as 88V, indicating some cells are reversed, contributing a negative emf.
Step 2: Calculate the number of reversed cells.
Let be the number of reversed cells.
The emf contributed by the reversed cells is .
Thus, the total emf is: Solving for :