Introduction:
Electrical transducers are devices that convert one form of energy into electrical signals. They play a crucial role in various applications, such as in measuring physical quantities, monitoring biological signals, and detecting chemical changes. In this question, we are asked to identify the type of signals generated by electrical transducers.

Explanation:
Electrical transducers are designed to convert different types of energy into electrical signals. Let's discuss the options given in the question and find out which one is correct.

a) Biological signals:
Biological signals are generated by living organisms and are typically in the form of electrical impulses, such as the signals produced by the brain, nerves, or muscles. While electrical transducers can be used to measure and record biological signals, they do not generate biological signals themselves. Therefore, option 'a' is incorrect.

b) Chemical signals:
Chemical signals are molecular messengers that carry information between cells or organisms. These signals can be in the form of hormones, neurotransmitters, or other chemical substances. Electrical transducers can be used to detect and measure chemical changes, but they do not generate chemical signals. So, option 'b' is incorrect.

c) Physical signals:
Physical signals refer to various forms of energy, such as mechanical, thermal, or electromagnetic signals. Electrical transducers can be used to convert these physical signals into electrical signals. However, they do not generate physical signals themselves. Therefore, option 'c' is incorrect.

d) Electrical signals:
Electrical transducers are specifically designed to generate electrical signals. They convert energy from various sources, such as mechanical, thermal, or electromagnetic energy, into electrical signals. These electrical signals can be voltage, current, frequency, or any other electrical parameter. Therefore, option 'd' is the correct answer.

Conclusion:
Electrical transducers play a vital role in converting different forms of energy into electrical signals. While they can be used to measure and detect various types of signals, they themselves generate electrical signals. This makes option 'd' the correct answer.